A run chart, or run sequence plot, is a graph that displays observed data over time to identify patterns or anomalies. It plots the observed variable on the y-axis and time on the x-axis. A central reference line, like the median, is often included. Run charts are used to detect shifts or outliers in processes over time that could indicate factors influencing variability. They provide a simple way to visualize univariate time series data and identify changes without the control limits of statistical process control charts.