How to make a run chart
- Copy the measurement column, in measurement order, together with its header.
- Click the column header (A) in the data table and paste - the first line becomes the column name. You can also open a CSV or Excel file.
- Choose the Y-axis columns (several allowed) and, if needed, enter the upper (UCL) and lower (LCL) control limits.
- Press Draw and check the median line, points outside the control limits and the trend interpretation.
What is a run chart?
A run chart connects measurements in time (measurement) order with points and lines and adds a median reference line. Without calculating statistical control limits as a control chart does, it makes it easy to see whether values cluster on one side (runs), keep rising or falling (trends), or jump suddenly.
It is often used as a first look at a process or when there is too little data for a control chart. Upper and lower control limits set from specs or experience are drawn as red dash-dot lines.
The median line
Each series gets a dashed line at its median in the same color. Unlike the mean, the median is barely affected by extreme values, which makes it easy to judge whether points are evenly mixed above and below it.
How to read a run chart
- A long sequence of points on one side of the median (a run) suggests the process level has shifted.
- Points that keep rising or falling indicate a trend. The automatic interpretation reports a trend when the R² of a linear fit against measurement order is 0.5 or higher.
- Investigate and record the cause of any point outside the upper or lower control limit.
Frequently asked questions
How is a run chart different from a control chart?
A run chart only adds a median line to show the flow, while a control chart calculates statistical control limits (±3σ) from the data. Xbar-R, I-MR and other control charts are available in the Qstat desktop program.
Do I have to enter control limits?
No. Leave them blank to draw only the median line. If you enter them, red reference lines are drawn and the number of points outside them is reported.
Can I plot several columns together?
Yes. Select several Y-axis columns and each is drawn in its own color with its own median line.
Is my data sent to a server?
No. Everything is processed inside your browser and nothing is transmitted or stored.
Other chart tools
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