The Levey-Jennings quality control chart is a graphical representation of QC data used in the lab named after D.H. Levey and E.R. Jennings who developed the method. The chart is used to monitor the performance of an analytical method over time. Its purpose is to identify any systematic errors or changes in performance of the method. The chart is a widely used tool in lab QC, and can help ensure the accuracy and precision of test results.