A Run Chart is the most basic tool used to display how a process performs over time.
It is a line graph of data points plotted in chronological order—that is, the sequence in which process events occurred.
These data points represent measurements, counts, or percentages of process output.
Run Charts are used to assess and achieve process stability by highlighting signals of special causes of variation
When to use?
- Understand variation in process performance so you can improve it.
- Analyze data for patterns that are not easily seen in tables or spreadsheets.
- Monitor process performance over time to detect signals of changes.
- Communicate how a process performed during a specific time period.
Using Run Charts can help you determine whether your process is stable (free of special causes), consistent, and predictable.
Unlike other tools, such as Pareto Charts or Histograms, Run Charts display data in the sequence in which they occurred.
This enables you to visualize how your process is performing and helps you to detect signals of special causes of variation.
How to use?
Run Chart is made up of seven parts:
- Title: The title briefly describes the information displayed in the Run Chart.
- Vertical or Y-Axis: This axis is a scale which shows you the magnitude of the measurements represented by the data.
- Horizontal or X-Axis: This axis shows you when the data were collected. It always represents the sequence in which the events of the process occurred.
- Data Points: Each point represents an individual measurement.
- Centerline: The line drawn at the median value on the Y-axis is called the Centerline. (Finding the median value is Step 3 in constructing a Run Chart.)
- Legend: Additional information that documents how and when the data were collected should be entered as the legend.
- Data Table: This is a sequential listing of the data being charted.