The Levey-Jennings chart is a graph used in labs to monitor how well a test is performing over time. The graph has horizontal lines that show the expected range of variation for test results, and a central line that represents the average result. When new test results are plotted on the graph, if they fall within the expected range, they’re considered acceptable. The chart helps lab staff spot patterns in test results that could indicate issues with the testing process. By spotting these patterns, lab staff can take steps to improve the testing process and make sure the results are accurate.