A simple monthly means chart system for monitoring sperm concentration

A simple, robust monthly means chart system for monitoring sperm concentration was developed and used in our andrology laboratory. The system relied on the central limit theorem to allow estimation of chart limits without resorting to data transformation procedures. Once the chart was drawn up, the arithmetic mean of sperm concentration was determined monthly and plotted. Monthly means which fell outside 2 SE from the baseline mean were investigated. Initial experience with this chart system suggests that it provides a simple and useful quality assurance method which should be applicable to other semen variables such as motility and sperm morphology.