Which of the following describes the regression effect in the context of internal validity?

The regression effect, particularly in the context of internal validity, refers to the phenomenon where individuals with extreme scores (either very high or very low) tend to move closer to the mean upon subsequent measurements. This occurs because extreme outcomes are often influenced by random fluctuations or measurement error, rather than a stable trait or characteristic.

For example, if a group of students performs exceptionally well on a test due to a particularly easy version, their performance may not be replicated on a subsequent test, and their scores are likely to regress toward the average level of achievement. This effect is crucial in research as it can impact the interpretation of results and may lead researchers to incorrectly attribute changes in behavior or performance to an intervention, rather than to this natural statistical phenomenon. By recognizing and accounting for the regression effect, researchers can better maintain the internal validity of their studies.