The Levey-Jennings Quality Control Chart is a graphical tool used in statistical process control (SPC) to monitor the stability and consistency of a process over time. It is commonly used in laboratory and clinical settings to track the performance of analytical methods or instruments. The chart displays control limits, typically set at +/- 2 or 3 standard deviations from the mean, along with plotted data points from daily or periodic quality control samples. By visually analyzing the chart, technicians can quickly identify trends, shifts, or outliers that may indicate a change in the process or instrument performance, allowing for timely corrective action to be taken.