What should be plotted on the x-axis of a run chart to visualize performance over time?

The x-axis of a run chart should be plotted with time as it allows for the visualization of how a particular measure changes over a specified period. By placing time on the x-axis, you can track trends, patterns, and variations in performance, making it easier to identify points in time where improvements or declines occur.

This format enables teams to analyze the impact of interventions or changes in processes, helping to correlate those changes with specific time frames. Observing performance over time is crucial in quality improvement as it provides insights into whether the implemented changes are leading to sustainable improvements or if adjustments are needed.

The other options represent important factors that can be analyzed but do not serve the purpose of displaying temporal data, which is the primary function of a run chart. By focusing on time on the x-axis, the run chart becomes an effective tool for identifying trends and variations that could inform quality improvement efforts.