A Run Chart, also known as a run-sequence plot, is a simple line graph that displays process performance data over time. Its primary purpose is to help identify trends, patterns, or shifts in a process that might not be otherwise apparent. It is one of the seven basic tools of quality.
Key Aspects of a Run Chart
- Time Series Data – It always plots a specific performance metric (on the Y-axis) against time (on the X-axis).
- Identifies Trends and Patterns – It is used to visually detect non-random patterns in data, such as sustained upward or downward trends, or cyclical patterns.
- Simplicity – It is one of the easiest quality tools to create and interpret, making it highly accessible.
- Precursor to a Control Chart – A run chart is often a simpler version of a control chart; it shows variation over time but does not have statistically calculated upper and lower control limits.
How to Read a Run Chart
| Component | Description | Purpose |
|---|---|---|
| X-Axis (Horizontal) | Represents time or the sequence of events. | Shows the chronological order of the data points. |
| Y-Axis (Vertical) | Represents the measurement or performance metric being tracked. | Shows the magnitude of the metric at each point in time. |
| Data Points | Individual measurements plotted on the chart. | Represent the performance of the process at a specific moment. |
| Median Line | A horizontal line drawn at the median of all the data points. | Serves as a centerline to help identify non-random patterns more easily. |
Example Scenarios
Tracking Software Defects
A software development team uses a run chart to plot the number of new bugs reported each day. After implementing a new code review process, they watch the run chart to see if there is a sustained downward trend in the number of daily defects.
Monitoring Project Schedule Performance
A project manager tracks the Schedule Performance Index (SPI) on a weekly basis using a run chart. This allows them to quickly see if the project’s schedule efficiency is trending up, down, or staying stable over time.
Agile Team Velocity
A Scrum team plots their velocity (the number of story points completed) at the end of each Sprint. The run chart helps them visualize if their performance is becoming more consistent or if there are unusual patterns (e.g., a dip in velocity every third Sprint).
Why Run Charts Matter
- Provides Early Warning Signs – They can reveal that a process is changing or drifting before it becomes a major problem.
- Visualizes Process Performance – They make it easy to see and communicate how a process is performing over time.
- Helps Evaluate Improvements – They are an excellent tool for tracking the impact of a process change to see if it resulted in a measurable improvement.
- Simple yet Powerful – It is a foundational quality tool that provides significant insight with minimal complexity.
See also: Control Chart, Seven Basic Quality Tools, Quality Management, Process Improvement.