What phenomenon refers to the tendency for extreme scores to move closer to the average over time?

The phenomenon where extreme scores tend to move closer to the average over time is known as regression toward the mean. This concept is grounded in the principle of variability and is often observed in various fields such as psychology, education, and sports.

When analyzing data, particularly with repeated measurements, extreme values are likely influenced by many factors, including random chance. Over time, as more data points are gathered or as the measured subjects experience variations in conditions, the results tend to stabilize around the average, resulting in extreme values moving closer to that average. This doesn't imply that the mean itself changes but rather that the extreme values reflect a return to a more central tendency as other influencing factors balance out.

In contrast, other terms such as skewed distribution refer to how data is spread in relation to the mean, suggesting an asymmetrical arrangement rather than a movement towards it. Bimodal distribution refers to a distribution with two different modes or peaks, indicating multiple prevalent values, which does not inherently suggest movement towards the average. Statistical significance is a measure of whether the results of an analysis are likely not due to chance, rather than describing a phenomenon concerning the values themselves and their relationship to the mean.