What best describes a control chart?

A control chart is fundamentally a graphical tool used to monitor the variation in a process over time. It allows practitioners to observe data points plotted in time order, which makes it possible to identify trends or patterns in the process being monitored. The primary purpose of a control chart is to determine whether a process is in a state of statistical control or if there are variations that may indicate a problem that needs to be addressed.

By plotting data points against control limits, which are usually set at three standard deviations above and below the mean of the data, control charts help distinguish between common cause variation (natural fluctuations inherent in the process) and special cause variation (indicating an abnormal issue). This is crucial in quality management and performance improvement efforts as it enables teams to take proactive measures to maintain or improve the quality of processes.

In contrast, other options describe different tools or standards that serve distinct purposes. For instance, visualizing patient flow focuses on operational efficiency, demonstrating compliance relates to adherence to regulations, and coding accuracy refers to standards in coding practices—all of which do not capture the essence of what a control chart is designed to accomplish in monitoring process variation.