Regression Toward the Mean in Fertility Research - An Empirical Study of Semen Quality

Abstract
Regression toward the mean denotes circumstances, where extreme observations tend to normalize at repetition. The phenomenon is caused by random variation and may occur whenever mainly persons with extreme values are subject to repeate examinations. We furnish empirical evident that the phenomenon may be quantitatively important in fertility research with regard to some, but probably not all indicators of semen quality.