Factors Affecting Haemocytometer Counts of Sperm Concentration in Human Semen

Summary. Each of three technicians made duplicate pipettings from forty-six semen specimens ofseven donors and filled two haemocytometer chambers from each pipette. The number of spermatozoa in each of the four large corner squares of the chamber were counted and recorded separately for a total of 2208 counts on 552 chambers. An analysis of variance was made and the percentage variances were calculated. Marked variation was found in counts among technicians and in dupli-cate counts by the same technician. The technician term and the related technician interaction terms accounted for 14\=.\\8of the total study variance. Approximately one-halfof the variance of the haemocytometer technique itself was due to the variance among technicians (57\=.\\4%) and one-half to the variance among duplicate haemocytometer determin-ations by the same technician (42 \=.\\6%). The 95 % confidence interval for haemocytometer counts, among technicians, on a single specimen which is equal to the mean of this study (28 million/ml), is \=+-\\52%. The vari-ance associated with the haemocytometer technique is large and must be considered in the design and analysis of studies of semen.