The Concept of Reversion to Mean in Project Management

The Concept of Reversion to Mean in Project Management
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In everyday life we experience abnormalities all the time. Consider fluctuations in the weather and the occurrence of above average temperatures, often followed by periods of below average temperatures. Consider that periods of extraordinary decreases typically follow periods of extraordinarily high stock market gains. Even consider that your body may experience periods of added pain, discomfort or stiffness, followed by periods of much better feelings without any medical intervention.

Indeed, the occurrence of what we might call “abnormal” is, well, normal!

But the lesson is that, without any intervention from us, experiences out of the ordinary will tend to move back toward the norm.

Reversion to Mean

And there is a term for this – reversion to mean.

What this means is that we need to be careful about what action we consider in light of the data at hand. Here are a few applications in the realm of project management:

  1. On your project, you may see abnormally high or low work completion rates. It is good to have the information – and to get advance indicators – but beware of reacting too quickly, because it is likely that these performances will revert to the mean. It’s most important to identify if there might be a shift in the mean!
  2. You may observe that there are periods of a lot of meetings, and periods of few meetings. Be aware that these could be anomalies…and that observations will tend to revert to the mean, or normal, level of meetings. Again, the thing to look for is a shift in the mean.
  3. As a general observation, on our projects there are periods of seeming continual crisis, and other periods of seeming permanent calm. Recognize that even these observations will revert to mean…where you experience a stable occurrence of manageable crises and calm. Be alert, however, for a shift in the mean.

What areas of your project might appear to be out or the ordinary…and might simply revert to mean? Could it be possible that the man is shifting?

This post is part of the series: Project Management Thinking Traps

A series of four articles on thinking traps and the ramifications for Project Managers. Each of these traps can jade our thinking, but understanding the potential trap can empower us to be more effective leaders and decision makers and have a more positive impact on our projects.

  1. PM Thinking Trap: Obeying and Respecting Authority
  2. PM Thinking Traps: Reversion to Mean
  3. PM Thinking Traps: The Paradox of Choice
  4. PM Thinking Traps: “Because” Justification