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Sunday, October 11, 2026

Managing by Exception: Extending the Area of Normal Functioning to Corporate Teams

Exploring how ANF and SETDS can complement Agile, Kanban, and established management practices through statistical analysis and capacity forecasting

Introduction: From Technical Systems to Human Organizations

Throughout my career in IT Performance and Capacity Management, I have worked on a recurring problem: how to identify meaningful changes in complex systems without overwhelming administrators with unnecessary information.

This problem led me to develop the Statistical Exception and Trend Detection System (SETDS), along with methods for exception detection, change-point analysis, trend recognition, and forecasting.

The underlying management principle was relatively simple:

Do not intervene merely because something changes. Intervene when the change is meaningful.

This principle became central to my approach to Exception-Based Management.

More recently, while developing the broader concept of the Area of Normal Functioning (ANF), I began considering whether the same statistical principles could help us better understand corporate teams and organizational workloads.

What if we treated a team's workload as a dynamic system with its own normal operating range?

Could we distinguish ordinary fluctuations from meaningful structural changes? Could we anticipate emerging capacity problems? And could we reduce unnecessary managerial intervention while preserving team autonomy?

Initially, these possibilities appeared to offer a substantially different approach to organizational management.

However, examining established management frameworks reveals an important fact: many of these ideas already have significant precedents.

Agile emphasizes self-management and adaptation. Kanban provides quantitative flow metrics and forecasting. Statistical Process Control distinguishes common variation from exceptional conditions. PRINCE2 explicitly incorporates management by exception.

This raises a more interesting research question.

Rather than attempting to replace these approaches, could ANF provide an additional analytical framework that integrates statistical exception detection, structural change recognition, business-demand modeling, and proactive capacity forecasting?

I believe this possibility deserves further investigation.

1. Not Every Change Requires Management Intervention

Consider a software engineering team.

During one week, the team completes 25 tasks. During another, it completes only 19.

A manager looking at a conventional productivity dashboard might immediately question the decline.

But is there really a problem?

Perhaps the second week involved more complex tasks, unexpected technical difficulties, or necessary architectural improvements.

A single measurement rarely tells the whole story.

In technical systems, distinguishing normal variation from meaningful change has been studied for decades.

Statistical Process Control (SPC), originating in Walter Shewhart's pioneering work, introduced the distinction between common-cause and special-cause variation.

Thomas Nolan and Lloyd Provost, in their 1990 article Understanding Variation, emphasized the importance of this distinction for management decisions. They also explained why unnecessary adjustments to stable processes can actually increase variation.

The same principle applies to corporate teams.

Not every temporary decline in output represents a productivity problem. Not every increase in workload means that a team is approaching exhaustion.

We need to understand behavior over time.

This is where the ANF concept becomes relevant.

Instead of comparing every measurement against a fixed target or simple historical average, we can estimate a range of normal functioning based on observed behavior.

Suppose a team historically completes between 18 and 28 comparable work items per week.

Completing 19 items may be entirely consistent with normal variation.

A sustained decline to 12 items, however, could indicate a meaningful change requiring investigation.

The management principle becomes:

Normal variation should generally be tolerated. Meaningful deviations should be investigated, not automatically punished or corrected.

This is not a new management philosophy. What interests me is whether ANF and SETDS could provide an integrated statistical mechanism for implementing it.

2. What Existing Management Frameworks Already Offer

Before discussing the potential contribution of ANF, it is important to recognize the existing approaches.

Agile and Scrum: Autonomy and Adaptation

Agile principles emphasize sustainable development, teamwork, and responsiveness to change.

Scrum builds on transparency, inspection, and adaptation. It also recognizes teams as self-managing.

This philosophy is compatible with the objectives of ANF-based management.

Both approaches recognize that continuous external intervention is not necessarily productive.

However, Scrum does not prescribe a particular statistical method for calculating normal workload boundaries, detecting structural changes, or forecasting when team capacity constraints may emerge.

Such analytical methods could complement Scrum without changing its underlying philosophy.

Kanban: Managing the Flow of Work

Kanban is particularly relevant to the proposed application.

The May 2025 Kanban Guide identifies four fundamental flow metrics:

  • Work in Progress (WIP).

  • Throughput.

  • Work Item Age.

  • Cycle Time.

Kanban also supports probabilistic Service Level Expectations based on historical observations.

These metrics already provide valuable information about workload, predictability, and bottlenecks.

Furthermore, tools such as Jira include control charts displaying cycle times, rolling averages, and variability.

Therefore, introducing statistical charts into team management is not, by itself, a new contribution.

The research opportunity lies in investigating whether ANF/SETDS could add value through the integration of change-point detection, dynamically estimated operating boundaries, and forecasting of future operational constraints.

PRINCE2: Management by Exception

Another particularly relevant predecessor is PRINCE2.

Its Manage by Exception principle allows authority to be delegated within agreed tolerances.

When a project is expected to exceed these tolerances, the appropriate management level becomes involved.

This is conceptually close to the approach I have described as Exception-Based Management.

PRINCE2 also recognizes the importance of forecasting potential tolerance breaches before they occur.

An important distinction, however, is that project management tolerances are generally defined according to agreed objectives and constraints.

The ANF concept introduces a different type of boundary: one statistically estimated from observed system behavior.

These two types of boundaries should not be confused.

Statistical ANF boundaries describe what has historically occurred. Management tolerances describe what is considered acceptable.

Combining these perspectives could provide useful additional information for management decisions.

Statistical Process Control: A Common Foundation

Perhaps the closest methodological predecessor is Statistical Process Control.

SPC already provides methods for recognizing significant deviations from stable process behavior.

My SETDS work belongs to this broader tradition of statistical performance analysis, with particular emphasis on exceptions, change points, trends, and forecasting.

The proposed organizational application should therefore be understood as an extension and integration of established statistical ideas rather than a claim that statistical management itself is new.

The central research question is whether this particular combination can provide useful capabilities beyond those already available in conventional management analytics.

A Note About Terminology

There is also a terminology issue worth clarifying.

I have used Exception-Based Management to describe my management approach. However, Scrum.org already uses the abbreviation EBM for its distinct Evidence-Based Management framework.

Although the concepts are related through their reliance on information for management decisions, they are not the same methodology.

To avoid confusion, I will use ANF-based management or the full phrase Exception-Based Management when discussing my proposed approach.

3. From Reactive Management to Dynamic ANF Analysis

Having recognized these predecessors, we can formulate the proposed ANF application more precisely.

I envision it as an analytical layer that could complement existing organizational management frameworks.

Its potential value would come from combining four capabilities.

First: Estimating the Area of Normal Functioning.

Historical observations can be used to estimate a typical range of operating behavior.

Depending on the analytical method, boundaries might be represented by statistical control limits or distribution quantiles, such as P05 and P95, with P50 representing the median.

These methods have different statistical interpretations and should not be treated as interchangeable.

The purpose is to understand expected variation rather than using a single fixed target as the only acceptable value.

Second: Detecting meaningful changes.

A team may experience an abrupt shift following a product launch, organizational restructuring, or significant change in business demand.

Change-point analysis could help identify when the underlying behavior has changed.

The normal operating range may then need to be reassessed.

Third: Recognizing developing trends.

Not all important changes happen suddenly.

Incoming work, cycle time, or backlog may increase gradually while individual measurements remain within their historical ranges.

Trend analysis can help distinguish persistent movement from short-term fluctuations.

Fourth: Forecasting future constraints.

When a persistent trend is identified, forecasting methods may estimate when an operational threshold will be approached or crossed.

This is an extension of the time-to-threshold forecasting approach I have used in technical Capacity Management.

Together, these capabilities could support a more proactive form of workload analysis.

Importantly, none of these techniques individually constitutes a new invention in organizational management.

The proposed contribution lies in their integration through ANF and SETDS, and in evaluating whether that integration improves management decisions.

3.1. A Practical Illustration: IT-Control Chart of a Team's Weekly Workload

To illustrate this idea, I created a hypothetical example using synthetic workload observations for a software engineering team.

The example covers 60 weeks: 52 observed weeks and an eight-week forecasting horizon.

Rather than using completed story points as a proxy for workload, I use estimated effort-hours associated with incoming work.

This distinction is important.

Completed story points describe delivery estimates, not necessarily incoming demand, actual employee working hours, or sustainable team capacity.

Estimated effort-hours are also imperfect measurements, but they allow us to illustrate how changing demand might be compared with a separately estimated processing-capacity limit.

Figure 1. ANF-based IT-Control Chart of a hypothetical software engineering team's weekly incoming workload. The chart shows observed demand (black), retrospectively estimated statistical ANF boundaries (P05 in blue, P50 in green, P95 in red), a shaded normal-functioning range, a simulated change in operating conditions, and a linear forecast. The orange dashed line represents an independently assumed processing-capacity limit of 185 estimated effort-hours per week. All observations are synthetic.


Figure 1. ANF-based IT-Control Chart of a hypothetical software engineering team's weekly incoming workload. The chart shows observed demand (black), retrospectively estimated statistical ANF boundaries (P05 in blue, P50 in green, P95 in red), a shaded normal-functioning range, a simulated change in operating conditions, and a linear forecast. The orange dashed line represents an independently assumed processing-capacity limit of 185 estimated effort-hours per week. All observations are synthetic.

The chart illustrates three periods.

Period 1: Normal Functioning (Weeks 1–20)

During the initial period, incoming workload fluctuates around a relatively stable level.

The retrospective statistical baseline is:

  • Lower ANF boundary (P05): approximately 127.5 effort-hours per week.

  • Median (P50): approximately 133.8 effort-hours per week.

  • Upper ANF boundary (P95): approximately 140.4 effort-hours per week.

Most observations remain within the estimated normal-functioning range.

This variation does not necessarily require corrective intervention.

The team can continue operating autonomously while managers maintain regular communication, support, and oversight.

Period 2: A New Operating Regime (Weeks 21–40)

Beginning around Week 21, the synthetic example introduces an increase in incoming demand.

This represents a hypothetical business event, such as a product launch or the acquisition of additional customers.

The team begins operating at a higher workload level.

Using a sample from the new regime (Weeks 24–39), the retrospectively estimated ANF becomes:

  • P05: approximately 143.4 effort-hours per week.

  • P50: approximately 150.7 effort-hours per week.

  • P95: approximately 160.2 effort-hours per week.

This illustrates an important feature of dynamic systems: their normal operating conditions can change.

However, we must distinguish a statistically established new baseline from a healthy or sustainable one.

A manager should investigate whether the team has adapted successfully through automation, process improvements, or additional resources—or whether it is absorbing the extra demand through excessive effort.

The statistical change does not answer that question by itself.

Period 3: Increasing Demand and Capacity Forecasting (Weeks 41–60)

After Week 40, the synthetic workload begins increasing more rapidly.

Several observations exceed the previously estimated upper ANF boundary.

The repeated deviations suggest that the earlier operating regime may no longer adequately describe current conditions.

For illustration, I fitted a simple linear trend to the observations from Weeks 41–52.

The resulting trend increases by approximately 1.84 estimated effort-hours per week.

If that trend continues without intervention, the forecast reaches the assumed processing-capacity threshold of 185 effort-hours per week around Week 57.

This is a conceptual example of Time-to-Threshold Forecasting applied to an organizational system.

Instead of waiting until backlogs accumulate or delivery deadlines are missed, management could investigate the trend and consider adjusting priorities, improving processes, or increasing available resources.

However, several methodological limitations must be emphasized.

First, the change in demand was deliberately introduced into the synthetic dataset. It was not independently discovered by SETDS.

Second, the ANF boundaries are empirical percentiles calculated retrospectively from selected operating periods. They are not classical Shewhart control limits, nor do individual percentile exceedances automatically establish statistical significance.

Third, the forecast is a simple linear regression extrapolation. It does not include uncertainty intervals, future changes in demand, or the effects of management intervention.

Finally, the 185-hour threshold is an assumed operational planning limit. It is not a medically or psychologically defined burnout threshold.

What Does This Example Demonstrate?

Despite its simplified nature, the example illustrates three different analytical questions:

Normal variation: Is the observed workload consistent with an established operating regime?

Structural change: Has the behavior of the system changed enough to justify reassessing its statistical baseline?

Future constraints: Does the developing trend suggest that operational demand may exceed available processing capacity?

The example also highlights why analyzing incoming workload alone is insufficient.

A practical organizational application would need to examine incoming demand together with completed throughput, backlog, cycle time, available resources, and relevant quality indicators.

The real opportunity for ANF-based management is to integrate these perspectives, not to replace them with a single workload chart.

4. Connecting Business Demand to Team Capacity

Another possible extension comes directly from my earlier work in IT Capacity Management.

In technical systems, resource requirements often depend on measurable business drivers.

For example, we may model how transaction volume affects CPU utilization, memory consumption, or response time.

The objective is to establish empirical relationships between business activity and technical resource demand.

A similar approach could be investigated for corporate teams.

Consider a customer onboarding department.

Its workload may depend on several factors:

  • Number of new customers.

  • Complexity of onboarding requirements.

  • Number of products or services involved.

  • Amount of manual processing.

  • Availability of automation.

  • Experience and skills of the team.

Suppose historical observations suggest that onboarding ten additional customers is associated with approximately 15 extra hours of team effort under comparable conditions.

Such a relationship could help estimate future resource requirements.

However, organizational systems are more complex than technical infrastructure.

The relationship may change when new software is introduced, employees gain experience, processes are redesigned, or customer requirements become more complicated.

Therefore, a useful model should not assume that historical relationships remain constant indefinitely.

This is where change-point detection and dynamic model reassessment could become particularly valuable.

Instead of relying on a permanently fixed relationship between business demand and team effort, we could investigate how that relationship evolves.

I see this as a possible continuation of my earlier exception-based capacity modeling work.

The objective would not be to mechanically determine how many employees a company must hire.

It would be to provide quantitative evidence to support resource planning and managerial judgment.

5. The Human Difference: Statistical Normality Is Not Sustainability

At this point, an essential distinction must be made.

Corporate teams are not server clusters.

Although statistical methods may be applied to observable organizational behavior, people cannot be managed as interchangeable technical resources.

Human performance depends on motivation, skills, fatigue, interpersonal relationships, organizational culture, and many other factors.

A team might maintain high output because its members have become more experienced and efficient.

The same output might also be sustained through excessive overtime and growing exhaustion.

Operational statistics alone may not distinguish these situations.

An additional problem arises when historical behavior itself is unhealthy.

Imagine a department whose employees have consistently worked excessive hours for several years.

A statistical model might identify this workload as normal because it has become the established operating pattern.

But statistically normal does not necessarily mean healthy, desirable, or sustainable.

This distinction is fundamental to extending ANF into human systems.

I would therefore separate two types of boundaries.

Statistical ANF boundaries describe the range of observed behavior under a particular operating regime.

Organizational sustainability boundaries represent conditions considered acceptable based on available resources, operational goals, working conditions, employee feedback, and relevant research.

These boundaries are not necessarily identical.

This also connects ANF to existing research in organizational psychology.

For example, Job Demands–Resources (JD-R) theory examines relationships among workplace demands, available resources, burnout, and engagement.

Similarly, the SPACE framework for developer productivity emphasizes that productivity cannot be represented adequately by a single metric. It includes dimensions such as satisfaction, well-being, performance, communication, and efficiency.

These frameworks provide perspectives that a purely statistical ANF model would not capture on its own.

A meaningful organizational application should therefore complement established human-centered research.

It should also prioritize team-level measurements where practical, protect employee privacy, and avoid turning exception detection into individual surveillance.

6. A Different Role for the Manager

What would this mean for a corporate manager?

I do not believe the goal should be automated management in which statistical models decide when human intervention is permitted.

A manager has responsibilities that cannot be reduced to quantitative monitoring.

These include coaching, resolving conflicts, supporting professional development, understanding employee concerns, and creating an effective working environment.

However, statistical analysis could help managers devote less attention to routine fluctuations and more attention to meaningful issues.

Three activities become particularly important.

Understanding Exceptions

When a significant deviation occurs, the first response should be investigation rather than blame.

Is the change caused by business demand, staffing, task complexity, process inefficiency, or an improvement in productivity?

An exception should initiate a question, not automatically trigger a corrective action.

Anticipating Constraints

Trend analysis and forecasting could help identify emerging problems before they become operational crises.

If incoming demand consistently grows faster than throughput, a manager may have time to adjust priorities or request additional resources.

Supporting Adaptation

When structural changes occur, teams may need to adapt.

Management should help determine whether the team can establish a sustainable new operating regime or whether the organization must change its expectations, resources, or processes.

In this interpretation, Exception-Based Management is not about reducing leadership to statistical alerts.

It is about using statistical evidence to support better judgment while preserving team autonomy.

7. Toward an Integrated Organizational ANF Framework

The organizational extension of ANF remains a research proposal.

My previous work provides a technical foundation in statistical exception detection, change-point analysis, trend recognition, and capacity forecasting.

The next challenge is to investigate whether combining these methods adds practical value to existing organizational management approaches.

A possible framework could contain five stages.

Stage 1 — Select meaningful operational measurements.

Use existing team-level information such as incoming demand, throughput, backlog, cycle time, and available processing capacity.

Avoid treating a single productivity metric as a complete description of team performance.

Stage 2 — Establish a statistical ANF.

Estimate expected operating behavior from historical observations, taking into account staffing changes, work complexity, seasonality, and other relevant conditions.

Stage 3 — Detect exceptions and structural changes.

Apply statistical methods to distinguish ordinary variation from potentially significant changes in system behavior.

Investigate whether a detected change represents improvement, deterioration, or adaptation to new conditions.

Stage 4 — Forecast operational constraints.

Analyze developing trends and estimate when relevant planning limits might be approached.

Keep these limits distinct from the statistical ANF boundaries.

Stage 5 — Support decisions and evaluate outcomes.

Combine statistical evidence with managerial experience, employee feedback, and organizational context.

Measure whether the approach improves the quality or timeliness of decisions.

The final stage is particularly important.

It would not be sufficient to demonstrate that an ANF model produces visually interesting charts.

A meaningful study should compare its results with existing methods.

For example, we could evaluate conventional fixed thresholds, established SPC techniques, Kanban-based flow analysis, and an integrated ANF/SETDS implementation using identical datasets.

Potential evaluation criteria could include detection delay, false-alert frequency, forecast accuracy, and the usefulness of the resulting information for management decisions.

Only such comparisons could establish whether the proposed integration offers measurable advantages.

8. What Might Be the Actual Contribution of ANF?

After examining existing management practices, I would formulate the research opportunity more carefully than I initially did.

Management by exception is not new.

Statistical control charts are not new.

Agile autonomy, Kanban flow metrics, and workload forecasting are not new either.

However, these concepts are frequently implemented in different contexts and for different purposes.

The possibility I would like to investigate is whether an ANF-based analytical layer can bring together:

  1. Statistical estimation of normal operating behavior.

  2. Detection of meaningful exceptions and structural changes.

  3. Recognition of evolving workload trends.

  4. Modeling relationships between business demand and operational capacity.

  5. Forecasting the time remaining before relevant constraints may be reached.

The specific contribution would depend on the methods implemented and their demonstrated performance compared with existing alternatives.

The central hypothesis is that integrating these analytical capabilities could improve the recognition of meaningful workload changes and provide earlier, more actionable information for management decisions.

This remains a research hypothesis, not an empirically validated conclusion.

The broader significance may lie in exploring how methods developed for technical performance management can be adapted to more complex organizational systems without ignoring their human characteristics.

Conclusion: ANF as a Complement to Existing Management Practices

My work on the Area of Normal Functioning began long before its recent applications to IT performance analysis.

The original concept emerged from my research into robotic grasping and passive adaptation.

Later, my work on SETDS and IT-Control Charts provided statistical approaches for examining normal behavior, detecting exceptions, identifying structural changes, and analyzing trends in technical systems.

Today, I am exploring whether this accumulated experience can contribute to understanding human and organizational systems.

Reviewing existing management practices shows that many of the underlying ideas already have well-established foundations.

Rather than diminishing the relevance of ANF, I believe this provides a more meaningful direction for further work.

ANF does not need to replace Agile, Kanban, PRINCE2, or Statistical Process Control.

It may instead provide a complementary analytical perspective, particularly where operating conditions change over time and future capacity constraints are important.

The objective is not to turn people into measurable components of a mechanical system.

It is to help leaders distinguish routine variation from meaningful change, recognize emerging constraints, and support organizational adaptation.

The principle remains consistent with my earlier technical work:

Do not react to every fluctuation. Understand what is normal, recognize when conditions meaningfully change, and anticipate future constraints before they become serious problems.

Whether an integrated ANF approach can improve corporate workload management remains an open research question.

But it is one I believe is worth investigating.


References and Further Reading

  1. Nolan, T. W., & Provost, L. P. (1990). Understanding Variation. Quality Progress, 23(5), 70–78. American Society for Quality.

  2. Schwaber, K., & Sutherland, J. (2020). The Scrum Guide. Official Scrum Guide.

  3. Kanban Guides. (2025). The Kanban Guide. Official Guide.

  4. Atlassian. View and Understand the Control Chart. Jira Software Documentation.

  5. PRINCE2. Understanding Tolerances in PRINCE2 Project Management. PRINCE2 Resource.

  6. Scrum.org. (2024). Evidence-Based Management Guide. Official Guide.

  7. Forsgren, N., Storey, M.-A., Maddila, C., Zimmermann, T., Houck, B., & Butler, J. (2021). The SPACE of Developer Productivity: There's More to It Than You Think. ACM Queue, 19(1). DOI: 10.1145/3454122.3454124.

  8. Bakker, A. B., Demerouti, E., & Sanz-Vergel, A. (2023). Job Demands–Resources Theory: Ten Years Later. Annual Review of Organizational Psychology and Organizational Behavior, 10, 25–53. DOI: 10.1146/annurev-orgpsych-120920-053933.


This article is part of my ongoing research and book project on the Area of Normal Functioning (ANF), exploring its applications across technical, AI, human, and hybrid systems.

Tuesday, September 29, 2026

Applying the Area of Normal Functioning (ANF) to Pharmaceutical Safety Data (#ANF #Pharmacovigilance #OpenFDA #AI #DataScience #ChangePointDetection #HealthcareAI #Pharma)

One of the goals of the Area of Normal Functioning (ANF) project is to test whether the same general framework can be applied across very different dynamic systems.

So far, I have been looking at ANF in technical systems, human behavior, sports and other time-dependent data. A natural next question is whether ANF can also be useful in pharmaceutical data.

A particularly interesting opportunity is pharmacovigilance — the analysis of adverse-event reports collected over time.

The basic idea is simple.

For a particular drug, we can construct a monthly time series of adverse-event reports and ask:

What does the normal reporting pattern look like, and when does that pattern change?

Instead of considering only whether a value is “high” or “low,” ANF attempts to characterize the range in which the system normally functions and then detect:

  • excursions outside that range;
  • persistent shifts;
  • change points;
  • new operating regimes;
  • trends that may eventually move the system outside its established ANF.

A promising first example is montelukast, marketed as Singulair.

The FDA has documented a history of neuropsychiatric safety concerns associated with montelukast. It issued communications beginning in 2008 and later required a boxed warning in 2020. This gives us something especially useful for methodological validation: known historical events that can be compared with change points detected independently from the data.

The proposed experiment would use monthly adverse-event data from the FDA Adverse Event Reporting System, available through openFDA.

Rather than analyze only the total number of reports, I would like to construct at least three related time series:

  1. total monthly montelukast adverse-event reports;
  2. monthly montelukast reports involving selected neuropsychiatric events;
  3. the ratio of neuropsychiatric reports to all montelukast reports.

The third series may be particularly useful because it can partially separate a change in the composition of reports from a general increase or decrease in overall reporting volume.

The main research question would be:

Can ANF and change-point analysis identify a structural change in montelukast adverse-event reporting without being told in advance when FDA communications occurred?

A strong version of the experiment would establish the initial ANF using only data available before 2008 and then process later observations sequentially.

That would let us ask a more interesting question:

At what point would the method first have indicated that the reporting process was no longer behaving within its previously established Area of Normal Functioning?

Detected change points could then be compared with known external events such as the 2008 FDA communication and the 2020 boxed warning.

It is important to be careful about interpretation. FAERS reports do not establish causality or true incidence rates. An increase in reports can result from many factors, including publicity, regulatory attention and stimulated reporting.

Therefore, the purpose of ANF would not be to conclude that a drug caused a particular effect.

The more defensible interpretation is:

ANF detects a change in the normal behavior of the pharmacovigilance reporting system.

Understanding why that change occurred is a separate analytical step.

This distinction is actually one of the reasons the example is interesting. ANF is designed to detect when a dynamic system moves into a different state, without assuming in advance what caused the transition.

If the experiment works well, I would next apply the same methodology to other known pharmaceutical events, such as the withdrawal of ranitidine and historical safety concerns around rosiglitazone.

Together, these examples could help determine whether ANF can provide a useful general framework for monitoring pharmaceutical and healthcare data in addition to technical and human systems.

Thursday, September 17, 2026

Can AI Systems Have an Area of Normal Functioning?

A synthetic TTFT experiment using dynamic ANF boundaries

As I continue developing the concept of the Area of Normal Functioning (ANF), I have been looking for new types of systems where the idea could be useful.

Artificial Intelligence - and particularly Large Language Model (LLM) services - provides an interesting case.

An AI system is still a system performing work. It receives a workload, consumes computational resources, produces results, and has measurable performance characteristics. That immediately raises a question:

Can we define an Area of Normal Functioning for an AI service?

I believe we can. 

Measuring the Performance of an LLM

Consider a user sending a request to an LLM. One particularly useful performance metric is Time to First Token (TTFT) - the time between submitting a request and receiving the beginning of the response.

For request i, we can write:

TTFTi = tfirst token - trequest

TTFT is affected by many factors, including workload, prompt size, concurrent requests, model characteristics, and available computing resources. Therefore, it should not be expected to remain constant.

Instead of asking whether TTFT is below some fixed threshold, ANF suggests another question: What range of TTFT values represents normal functioning of this particular AI system under its current operating conditions?

A Synthetic Experiment

To explore this idea, I generated a synthetic dataset representing 600 sequential requests to an LLM service. The simulated workload includes prompt and output token counts, changing levels of concurrent requests, an initially stable operating period, gradually increasing workload, a temporary overload period, and recovery into a somewhat different operating regime.

The TTFT itself was modeled conceptually as:

TTFTi = f(Pi, Ci) + εi

where Pᵢ is prompt size, Cᵢ is concurrent workload, and εᵢ represents normal random variability.

The objective was not to reproduce any particular commercial AI system. The dataset is deliberately synthetic so that the behavior of the system is known and the ANF concept can be demonstrated clearly.

Building the AI Area of Normal Functioning

For this initial experiment I used moving percentiles to describe the current operating region. For a rolling window of recent observations, the center line is:

CL(t) = P50(TTFT)

The lower and upper boundaries are:

LCL(t) = P05(TTFT)

UCL(t) = P95(TTFT)

Thus, the Area of Normal Functioning is:

ANF(t) = [P05(t), P95(t)]

The important point is that these boundaries are not fixed. They move as the behavior of the system changes.

Figure 1. Synthetic LLM service TTFT with a dynamic Area of Normal Functioning (P05-P95).


In the figure, the actual series represents TTFT; P50 describes the center of normal functioning; P05 and P95 form the lower and upper ANF boundaries; and the shaded region represents the Area of Normal Functioning.

The result is similar in spirit to the IT-Control Charts I have used for many years in computer performance analysis, but here the monitored object is an AI service.

Something Interesting Happens

During the first part of the experiment, TTFT fluctuates around a relatively stable level. As workload increases, however, both TTFT and its ANF begin moving upward. Eventually the simulated service enters an overloaded state. Its TTFT becomes substantially higher, but after enough observations the ANF itself adapts to this new operating regime.

An individual observation above the current upper boundary can be represented as:

TTFTt > UCL(t)

Such an observation may be an exception. Persistent movement of the entire ANF, however, can indicate something different: a change in the functioning of the system itself.

Exception  ->  Trend  ->  Change Point  ->  New ANF

From Detection to Prediction

The idea becomes even more interesting when trend analysis is added. Suppose the current TTFT trend can be approximated locally by:

TTFTpred(t) = a + bt

where b > 0 indicates increasing response latency.

If the current upper ANF boundary is UCL, the estimated crossing time is:

tcross = (UCL - a) / b

The corresponding time remaining before the forecasted ANF boundary crossing is:

TimeToANF = tcross - tnow

This changes the question from “Has AI performance become abnormal?” to the more useful proactive question: “How long do we have before AI performance is expected to leave its current Area of Normal Functioning?”

This connects ANF directly with proactive performance and capacity management.

Beyond TTFT

TTFT is only the first example. An AI service has many possible performance dimensions. A conceptual multidimensional formulation is:

ANFAI = f(TTFT, TPOT, Tokens/sec, QueueTime, TokenCount, Errors, ResourceUsage, ...)

Ultimately, an AI system may have a multidimensional Area of Normal Functioning rather than an ANF based on only one metric.

Even more interestingly, these dimensions are related. A TTFT that is unusual for a small prompt may be perfectly reasonable for a much larger request or under substantially greater concurrency. A more advanced formulation could therefore be conditional:

ANF = P(Performance | Workload, Model, Configuration)

In other words: What is normal performance for this AI system under these particular operating conditions? That is a much more interesting problem than simply comparing every request with a fixed threshold.

Why I Find This Interesting

ANF originated in my earlier work with technical systems. I am now exploring whether the same fundamental idea can describe normal functioning, adaptation, and change across very different kinds of systems.

AI creates an especially interesting bridge. It is clearly a technical computing system, making it suitable for traditional performance engineering. At the same time, modern AI increasingly interacts with people and becomes part of larger human-technical systems.

For now, this experiment is intentionally simple: one AI performance metric, synthetic data, and one-dimensional ANF analysis.

The logical next step is to repeat the experiment using real measurements from an LLM service. If the approach continues to work, ANF may provide a unified way to describe not only whether an AI system is functioning normally, but also how its normal state changes - and when it is about to leave it.

Note: This blog example uses synthetic data as a proof of concept. A future academic version should validate the method using measured LLM-serving telemetry and compare ANF-based detection with fixed SLOs and other adaptive baselines.


Tuesday, September 15, 2026

A YouTube Example of ANF: When “Typical Performance” Becomes a Normal Functioning Band

Sometimes the best examples of an idea appear in places where you do not expect them.

Recently, while looking at analytics for one of the videos on my YouTube channel @iTrubin, I noticed something that immediately reminded me of work I started more than twenty years ago.

YouTube now shows a “Typical performance” band around a video’s actual performance.

In the example below, the blue line shows the actual number of engaged views, while the gray area shows the range YouTube considers typical.

That immediately looked familiar to me.

This idea goes back to my SETDS work

In 2002, I published my first paper on SETDS — Statistical Exception and Trend Detection System at CMG’2002. That paper received the Best Paper Award.

The central idea was simple: a raw number by itself is often not very meaningful. What matters is whether that number is inside or outside the expected range of behavior.

This is how I approached IT performance data at the time.

Instead of asking:

“Is this value high or low?”

the more useful question was:

“Is this value normal for this system, at this time, under these conditions?”

That idea later became part of what I now describe more broadly as the Area of Normal Functioning — ANF.

And then I saw YouTube doing something very similar

I started my YouTube channel back in 2009. At that time, this kind of “typical performance” band was not part of YouTube Analytics.

Today it is.

YouTube compares the current behavior of a video with a range based on historical performance and presents that expected range visually.

For example, in the case shown here:

  • Engaged views: 44
  • Typical range: 10–50

and:

  • Views: 99
  • Typical range: 20–100

The raw values are useful, of course. But the ranges are much more informative.

Forty-four engaged views by itself tells me almost nothing.

Forty-four engaged views inside a typical range of 10–50 tells me that the video is performing toward the upper end of what is normal for this channel and this type of content.

That is a much richer interpretation.

Collective of Customers / Viewers as an ANF example. YouTube Analytics compares actual video performance with a “Typical performance” range. The example is based on analytics from my YouTube channel, @iTrubin.

Why I see this as an ANF example

What makes this particularly interesting to me is that the expected range is produced not by one viewer, but by the behavior of a collective.

A large number of viewers interact with content over time. Their combined behavior creates a statistical pattern.

That pattern becomes the “normal” or expected range.

So in this case:

the collective of viewers creates the Area of Normal Functioning, and the individual video is evaluated against it.

This is exactly the kind of extension of ANF that I find interesting.

Originally, I used similar ideas for computer systems and performance data.

Now the same way of thinking can be applied to:

  • customers,
  • viewers,
  • users,
  • athletes,
  • teams,
  • organizations,
  • and many other dynamic systems.

One important clarification

I am not suggesting that YouTube copied SETDS or used my work directly.

I did not patent SETDS, and I have no evidence of any connection.

What I find much more interesting is that similar analytical ideas appeared independently in commercial tools years later.

Over time, I have seen other products introduce concepts that looked familiar to me as well, and I have written about some of them on this blog.

For me, that is actually encouraging.

When the same basic concept keeps reappearing independently in different fields, it may be a sign that the underlying principle is useful and general.

From anomaly detection to normal functioning

My original SETDS work was mostly about finding exceptions, trends, and changes.

But over time, I became increasingly interested in the opposite side of the same problem:

What does normal behavior look like?

And more importantly:

How wide is the normal range, how does it change over time, and what happens when the system begins to move outside it?

That is one reason I now use the broader ANF concept.

The YouTube “Typical performance” band is a simple and very practical illustration of that idea.

It tells the creator:

“Here is where your content normally operates. Now let us see where this particular video falls relative to that area.”

That is ANF thinking in a very accessible form.

Final thought

The concept of an Area of Normal Functioning is not new in my work. I first introduced ОНФ/ANF decades ago in my PhD research on robotic grasping and passive adaptation.

Later, SETDS brought a related idea into statistical analysis of dynamic computer systems: instead of judging a measurement in isolation, define the expected range of behavior and detect meaningful departures from it.

What interests me now is how these lines of work come back together.

Seeing YouTube use a “Typical performance” band is interesting not because I believe there is any direct connection to my earlier work, but because it demonstrates how naturally the same principle appears in another domain.

Whether we are looking at a robotic grasp, a computer system, an athlete, a customer population, or millions of viewers, the underlying question is remarkably similar:

What is the Area of Normal Functioning for this system — and when does its behavior meaningfully move beyond it?

That is the broader idea I am now trying to develop with ANF.




Monday, September 14, 2026

Applying ANF to Clinical Exercise Data: HRV, Recovery, and Human Adaptation

In my recent posts, I explored how the Area of Normal Functioning — ANF — can be applied beyond computer systems.

I started with sport-performance data, including SoccerMon athlete-monitoring data and longitudinal runner training logs. Those examples showed that ANF can describe an athlete’s normal training-load range, detect unusual weeks, identify shifts in the normal regime, and even suggest possible training cycles.

This time I wanted to test ANF on a different kind of human-performance dataset: not competitive sport, but clinical exercise and recovery monitoring.

For this experiment, I used the ATOPE+Breast dataset, which contains daily monitoring records for breast-cancer patients during a therapeutic exercise intervention. The uploaded records.csv file includes daily fields for patient ID, study day, training-session information, HRV metrics, wellness self-reports, sleep, and activity/steps. The available fields include lnrmssd, recovery, fatigue, distress, sleep_satisfaction, sleep_time, Fitbit sleep fields, and step/activity metrics.

This makes the dataset especially interesting for ANF. The goal here is not athletic performance. The goal is safer human adaptation: how a patient responds to exercise, recovery, sleep, fatigue, and treatment context over time.

Why this dataset is different

In runner or soccer data, the main question is often about performance:

- Is the athlete training inside a normal load range?

In clinical exercise data, the question is different:

- Is the patient recovering and adapting within their own normal functional range?

That makes ANF potentially useful as a patient-specific monitoring layer. It does not diagnose medical problems, and it should not replace clinical judgment. But it can help highlight when a patient’s daily recovery or physiological state moves away from their recent normal pattern.

For a first proof of concept, I selected one patient with a relatively long daily history and built ANF charts using rolling percentile boundaries.

The model used:

  • rolling baseline from recent observations,
  • CL = P50,
  • UCL = P95,
  • LCL = P05,
  • gray band = ANF,
  • orange points = outside the ANF,
  • vertical markers = training-session days.

Chart 1 — LnRMSSD / HRV ANF

Figure 1. Patient-specific ANF for LnRMSSD, an HRV-based physiological recovery metric. The gray band shows the recent normal range; points outside the band indicate days outside the patient’s recent physiological recovery pattern.

The first chart uses LnRMSSD.

LnRMSSD means the natural logarithm of RMSSD, a common heart-rate-variability metric. In practical terms, it is often used as an indicator of autonomic recovery or physiological readiness.

For ANF, this is important because it gives us a more objective physiological signal than self-reported wellness alone.

In this chart, the ANF band represents the patient’s recent normal range of HRV-based recovery. A day below the lower boundary may suggest that the patient’s physiological recovery is lower than usual. A sustained downward movement may indicate stress, fatigue, treatment burden, poor sleep, or another contextual factor.

Of course, one point should not be over-interpreted. Human physiology is noisy. The value of ANF is not in treating one daily value as a diagnosis, but in showing how the patient’s recovery pattern behaves relative to their own recent baseline.

Chart 2 — Recovery Risk Index ANF

Figure 2. Patient-specific ANF for a recovery-risk index based on subjective recovery and wellness variables. Higher values indicate worse recovery state relative to the combined subjective indicators.

he second chart uses a combined recovery-risk index.

This index summarizes the subjective side of recovery: perceived recovery, fatigue, distress, and sleep-related state. The dataset includes daily self-reported variables such as recovery, fatigue, distress, sleep_satisfaction, and sleep_time.

This chart is interesting because it represents the “human feeling” side of the same process. HRV may show physiological recovery, but subjective wellness may show how the patient actually feels.

In ANF terms, the recovery-risk chart asks:

Is the patient’s perceived recovery state still within their recent normal range?

Days above the upper boundary may suggest unusually elevated recovery risk — for example, higher fatigue, lower perceived recovery, poorer sleep, or higher distress. Again, ANF does not explain the cause by itself. It highlights the departure from the patient’s own recent normal state.

Why the combination matters

The most interesting part is not either chart alone, but the idea of comparing them.

A patient may have:

  • normal HRV but poor subjective recovery,
  • low HRV but normal self-reported recovery,
  • both signals inside ANF,
  • or both signals outside ANF.

That combination may be more useful than a single metric.

For example, if HRV drops below normal and the recovery-risk index rises above normal, that may be a stronger signal that the patient is under unusual strain. If only one signal changes, the interpretation may require more context.

This is very similar to the way I previously connected business-driver metrics with computer-system metrics. A single signal is useful, but two related ANFs can provide a better diagnostic picture.

From sport performance to human recovery

This example broadens the ANF idea.

In the runner dataset, ANF described normal weekly training load.
In SoccerMon, ANF described athlete load and wellness/readiness.
In ATOPE+Breast, ANF describes patient-specific recovery and adaptation during therapeutic exercise.

That is an important step.

It suggests that ANF may apply not only to computer systems and athletes, but also to broader human recovery and rehabilitation contexts.

The common question remains the same:

What is normal for this system, at this time, and when has that normal changed?

First conclusion

This is still an exploratory proof of concept, but it is a useful one.

The ATOPE+Breast dataset shows that ANF can be applied to daily human recovery data, combining physiological, subjective, sleep, activity, and training-session information.

For me, the main takeaway is:

ANF can help describe a patient-specific area of normal recovery and adaptation.

This should not be interpreted as medical diagnosis. Instead, it is a monitoring and interpretation framework that may help clinicians, coaches, researchers, or patients notice when daily recovery patterns move outside the recent normal range.

In the broader ANF research direction, this dataset provides an important bridge:

  • from technical systems,
  • to sport-performance systems,
  • to clinical human adaptation and recovery.

That makes it a valuable addition to the future ANF paper.


Thursday, September 10, 2026

Applying ANF to Runner Training Data: Load Boundaries, Change, and Training Cycles

In my previous posts, I discussed the idea of the Area of Normal Functioning — ANF — as a way to describe how dynamic systems normally behave, when they move outside their normal range, and when their “normal” itself changes.

Most of my earlier work came from computer-system performance analysis: capacity, workload, anomalies, change points, and trends. But I am now exploring whether the same logic can be applied to human performance systems, especially sport-science data.

After my first ANF experiment with the SoccerMon dataset, I tried another open dataset: Injury Prediction for Competitive Runners.

Dataset source:
https://github.com/sonicjoy/Injury-Prediction-for-Competitive-Runners

For this first analysis, I selected one runner with a long usable history and focused on a simple metric:

weekly total kilometers (total kms)

In sport terms, this is a basic measure of external training load.

Building the ANF

For each week, I calculated ANF boundaries using the previous 12 weeks of data:

  • CL = rolling P50
  • UCL = rolling P99
  • LCL = rolling P01

The area between LCL and UCL represents the runner’s recent normal weekly load range.

This is important: the ANF is not fixed. It moves as the runner’s recent training pattern changes.

Figure 1 — Full-history ANF chart

The full chart shows that the runner’s normal weekly load was not constant. The ANF band moves up and down over time, reflecting changes in the runner’s typical training level.

This is already useful. Instead of looking only at isolated high or low weeks, ANF shows the evolving “normal” range of the athlete.

One especially interesting feature is the major downward shift late in the series. The actual weekly load drops, but more importantly, the ANF boundaries also move downward. In ANF terms, this means the runner’s normal load range changed.

This does not prove the cause. It could be related to injury, recovery, a change in training plan, seasonality, reduced availability, or another contextual factor. But the pattern is meaningful:

the runner was no longer operating within the same normal load range as before.

Figure 2 — Zoomed view of the late shift


The zoomed chart makes the late downward shift easier to see. Before the shift, the runner’s normal weekly distance was much higher. After the shift, both the center line and ANF boundaries moved to a lower level.

This is a good example of why ANF may be useful. It helps distinguish between:

  • a one-week anomaly,
  • a temporary fluctuation,
  • and a real change in the underlying functional regime.

I also reduced the sensitivity of change-point detection so that the chart highlights only major regime changes. This produced a cleaner and more interpretable result.

Possible oscillation and training cycles

Another interesting observation is that the ANF band seems to move in repeated waves. It does not simply drift randomly.

A preliminary periodicity check suggested a broad recurring cycle around 46 weeks, with additional medium-scale patterns roughly in the 28–40 week range.

I would not over-interpret this yet, but it may reflect:

  • seasonality,
  • training macrocycles,
  • buildup and recovery phases,
  • or repeated changes in the runner’s training plan.

This is an interesting extension of the ANF idea. ANF may help detect not only anomalies and change points, but also repeated shifts in the normal operating range of a human performance system.

Why this matters

In computer performance engineering, we often ask:

  • What is normal behavior?
  • When is the system outside normal limits?
  • Has the system changed?
  • Is there a trend?
  • Is there a recurring pattern?

The same questions can be meaningful for athlete data.

This runner example shows that ANF can describe:

  • a typical weekly load range,
  • unusually high or low load weeks,
  • a major downward regime shift,
  • and possible periodic training structure.

For me, the most important finding is not simply that the runner’s load dropped. The more interesting point is that the runner’s normal range moved downward.

That is exactly the type of behavior ANF is designed to capture.

First conclusion

This is still an exploratory analysis, but it provides another encouraging proof of concept for applying ANF beyond technical systems.

A runner, like a computer system, has a changing area of normal functioning. That area can expand, contract, shift, oscillate, or break.

Understanding those changes may be useful not only for performance engineering, but also for sport science, training analysis, and broader human-performance research.

Tuesday, September 8, 2026

Applying ANF to SoccerMon Data: A First Look at Load, Wellness, and Readiness

 As a first independent proof of concept, I applied the Area of Normal Functioning — ANF — idea to open SoccerMon athlete-monitoring data.

This work continues the broader ANF direction I described in my earlier post:
https://www.trub.in/2026/06/expanding-area-of-normal-functioning.html

The data source for this experiment is the open SoccerMon dataset:
https://zenodo.org/records/10033832

The goal was not yet to build a final predictive model. The goal was simpler: to see whether ANF can be defined from real sport-science data and whether it can help us interpret training load, wellness, readiness, and possible overload patterns.

For this first experiment, I selected one player with relatively complete longitudinal data. I built two weekly IT-control-style charts:

1.      Weekly training load

2.      Weekly wellness/readiness risk

Both charts use the same ANF logic. For each week, the athlete’s current value is compared with the previous 12 weeks of history.

The control limits are percentile-based:

·         CL = rolling median, or P50

·         UCL = rolling P95

·         LCL = rolling P05

The area between LCL and UCL represents the athlete’s recent Area of Normal Functioning.

Weekly load as external demand

The first chart looks at weekly training load. I calculated weekly load as the sum of daily load values within each week.

In ANF language, this chart shows the athlete’s normal range of external training demand. When weekly load stays inside the ANF band, it means the athlete is training within the range that has recently been normal for her.

When weekly load rises above the UCL, it means the athlete is experiencing a higher load than expected based on her recent history. This may indicate overload, an aggressive training ramp-up, or a temporary excursion beyond the normal functional range.

Several above-UCL weeks appeared in the data, especially during periods of rapid increase in training load. Some of these high-load excursions occurred near weeks with injury reports. This does not prove causality, but it suggests that the upper ANF boundary may be useful as an overload-warning signal.

The LCL is also shown for consistency. However, low-load excursions are harder to interpret. A week below the LCL may simply represent rest, tapering, recovery, disrupted training, or off-season behavior. In this first example, below-LCL weeks did not appear to align with injury reports.

So for training load, the upper boundary appears more informative than the lower boundary.

Wellness/readiness risk as internal response

The second chart looks at a composite wellness/readiness risk index.

This index combines normalized values of:

·         fatigue

·         soreness

·         stress

·         inverse readiness

·         inverse sleep quality

·         inverse mood

Higher values mean worse subjective condition or lower readiness.

This chart represents the athlete’s ANF for internal response rather than external demand. It asks a different question: not “how much work did the athlete do?” but “how did the athlete appear to be responding?”

Several weeks were above the wellness/readiness UCL. In ANF terms, these weeks suggest that the athlete’s subjective state moved outside her recent normal range. This may indicate reduced recovery, higher fatigue burden, elevated stress, or a temporary maladaptive state.

Interestingly, in this first sample, elevated wellness/readiness risk did not directly coincide with injury-report weeks. That is still useful. It suggests that wellness ANF may capture short-term internal state changes, while load ANF may better capture external stress. They are related, but not identical.

Why both charts matter

The most important lesson from this first experiment is that athlete ANF is probably multidimensional.

A player can have normal training load but poor wellness.
A player can have high training load but still report good readiness.
A player can show subjective stress without immediate injury.
A player can experience injury after load patterns that look unusual.

That means ANF should not be defined by one metric alone.

In sport, ANF may need at least two dimensions:

1.      External load — what the athlete is asked to do.

2.      Internal response — how the athlete appears to absorb and adapt to that load.

This is very close to the broader ANF idea: systems do not only have inputs; they also have internal state, adaptation capacity, boundaries, and delayed responses.

First conclusion

This SoccerMon experiment is still preliminary, but it supports the basic idea that ANF can be operationalized on real human-performance data.

The ANF framework allows us to ask:

When is training load normal for this athlete?

When is subjective wellness outside the usual range?

Is the athlete adapting, recovering, or moving toward overload?

Are we seeing noise, anomaly, change, trend, or possible breakdown?

This is exactly why sport science may be a promising first application area for ANF beyond technical systems. Athletes are living dynamic systems. They have individual boundaries, adaptation capacity, stress responses, recovery patterns, and changing normal ranges.

The next step should be to repeat this analysis across multiple players and test whether sustained or repeated departures from ANF boundaries are associated with injury, illness, poor recovery, or performance decline.