A system and method for determining a sigma of a clinical diagnostic process are disclosed. Specimen data are collected from a plurality of laboratory instruments. The specimen data are evaluated to determine a concentration and an analytical standard deviation for each data point. A clinical diagnostic process is run and patient analyte values are acquired, and a standard deviation is assigned to each patient analyte value based on the standard deviation of specimen data having a corresponding concentration. A single sigma-metric is computed based on the patient analyte assigned standard deviations, the sigma-metric representing the sigma of the clinical diagnostic process. The computed sigma-metric is reported to a user or laboratory manager.