True.
Studies that assign subjects to intervention groups based on their extreme scores are vulnerable to regression toward the mean. This phenomenon occurs because extreme scores are often due to measurement error, random fluctuations, or other factors that are not representative of the subject's true underlying ability or condition. When these subjects are retested, their scores tend to move closer to the mean, regardless of whether they receive an intervention or not. This can make it difficult to determine whether the intervention had any real effect, as any observed changes may simply be due to regression toward the mean.
To minimize the impact of regression toward the mean, researchers can use a variety of techniques such as random assignment, matching, or statistical adjustment. These methods help ensure that intervention and control groups are comparable at baseline, reducing the likelihood that differences in outcomes are due to chance or regression toward the mean.