Regression Toward the Mean

Regression toward the mean, or regression to the mean, is a statistical phenomenon that is often observed in student assessment and repeated measurements research in different branches of science. Regression toward the mean is present whenever a construct that is being measured is not accessible directly but is estimated by using methods that are not absolutely reliable. This is the case in the vast majority of measurements in social sciences, education, and students’ assessment. Observations with extreme values in the first measurement will tend to be closer to the mean in the second measurement, and extreme observations in the second measurement will tend to be closer to the mean in the first measurement, whenever two variables are not perfectly correlated.

Regression toward the mean must be ...