1. Within- and between-subject variation in semen parameters in infertile men and normal semen donors 
Brooks A. Keel, Ph.D., H.C.L.D.(A.B.B.) 
Fertility and Sterility 
Volume 85, Issue 1, Pages (January 2006)
DOI: /j.fertnstert
Copyright © 2006 American Society for Reproductive Medicine Terms and Conditions

2. FIGURE 1
Within-subject variation for sperm motility (top) and count (bottom). Semen analysis data are plotted consecutively for each of the 136 specimens produced by a single normal donor over a 4-year period. Dotted line represents the overall mean of the values, and solid lines represent ± 1 SD.
Keel. Variation of semen parameters. Fertil Steril 2006.
Fertility and Sterility  , DOI: ( /j.fertnstert )
Copyright © 2006 American Society for Reproductive Medicine Terms and Conditions

3. FIGURE 2
Within-subject coefficients of variation in sperm count (top left), motility (top right), velocity (bottom left), and semen volume (bottom right) from semen donors and patients as a function of age. Data obtained from all donors and patients were pooled and plotted against the respective age of the individual. Lines represent the linear regression and the 95% confidence interval.
Keel. Variation of semen parameters. Fertil Steril 2006.
Fertility and Sterility  , DOI: ( /j.fertnstert )
Copyright © 2006 American Society for Reproductive Medicine Terms and Conditions