Between and within subject correlations and variances for certain semen characteristics in fertile men.

Between subject and within subject variances and correlations for different semen characteristics have been determined for a population of 315 fertile men who provided one or more ejaculates within an abstinence period of 1 to 5 days. The semen characteristics measured were sperm count, semen volume, pre-freeze motility and post-thaw motility. An approach via a decomposition of the variance or via a decomposition of correlation leads essentially to the same conclusions i.e. the within subject factors are not negligible but are less important than the between subject ones. Thus there is broad evidence for overall differences in the quality of the ejaculate from one subject to the other but not for different ejaculates of the same subject.