Regression to Mean

Extreme events are naturally followed by less extreme events — not because of any intervention, but due to statistical reversion. We wrongly credit treatments for what is simply natural fluctuation.

• A golfer plays terribly, gets coaching, plays better — and credits the coach. The improvement was largely regression to their average.
• Patients visit a doctor at their sickest point. They improve. The doctor (and patient) credits the treatment — but they would have improved anyway.
• A CEO is hired after a catastrophic year. The company recovers. The CEO is called a turnaround genius — regression did most of the work.