A run chart is used to study collected data for trends or patterns over a specific period of time.
A run chart will help you:
- Monitor data over time to detect trends, shifts, or cycles
- Compare a measure before and after the implementation of solution to measure impact
- Focus attention on vital changes, not normal variation
- Track useful information for predicting trends
The run chart is a running record of a process over time:
- The vertical axis represents the process being measured
- The horizontal axis represents the units of time by which the measurements are made
- The center line of the chart is the mean or average
A run is defined as one or more consecutive data points on the same side of the mean line.
See Also: Control Chart
Creating a Run Chart
- Decide which data you will measure and track
- Gather data: Generally, collect 20-25 data points, with which you can detect meaningful patterns over time
- Create a graph on which you can plot your data (Y axis, or vertical line) over time (X axis, or horizontal line)
- Plot the data
- Interpret the chart: Focus on the vital changes or meaningful trends/patterns, rather than each and every data variation; keep reading for interpretation tips
Using a Run Chart: Testing for Special Causes
Test #1: The presence of too much or too little variability
- When there are too few or too many runs
Test #2: The presence of a shift in the process
- A special cause exists if a run contains too many data points (i.e., with 20 or more data points, a run of 8 or more data points is considered “too long”; with less than 20 data points, a run of 7 might also be considered “too long”).
Test #3: The presence of a trend
- A trend is defined as an unusually long series of consecutive increases or decreases in the data, (usually at least 6 or 7).
Isanti County: WIC No-Show Rate
In this chart, there are eight runs.
More Examples of Run Charts
|Woodall: The Use of Control Charts in Health-Care and Public-Health Surveillance (PDF: 316KB / 16 pages)|
|Mohammed, Worthington, and Woodall: Plotting Basic Control Charts: Tutorial Notes for Healthcare Practitioners (PDF: 663KB / 9 pages)|
|McCoy and Riley: Basics of the Control Chart (PDF: 220KB / 8 pages)|
|Public Health Memory Jogger
If you belong to a local health agency in Minnesota and would like a Memory Jogger free of charge, please contact the QI Unit.