Individuals and moving range chart
Control chart for single measurements (subgroups of one): the individuals chart with limits from the average moving range, and the moving range chart.
Menu: Graphs → More charts → Control chart: individuals, moving range…
When should I use it?
- Processes measured one value at a time (daily readings, batch results).
What are the assumptions?
- Values in time order; roughly normal; no strong trend or seasonality.
How do I run it in StatLab?
- Choose the measurement (and optionally a label variable).
How do I read the output?
| Output | Meaning |
|---|---|
| Individuals | Each value against limits at ±3 sigma, sigma = mean moving range / 1.128. |
| Moving range | Absolute difference between successive values. |
Worked example
On the practice survey dataset (File → Sample dataset), this command — which the dialog's Paste button also produces — runs the procedure:
PROC vizIMR /y=score /x='' /rules=YES.
Output tables: Rule Violations for Individuals · Rule Violations for Moving Range.
Computed by StatLab's validated procedure code when this page was built. The example only illustrates the steps; choose variables that fit your own research question.
What are common mistakes?
- Using it on trending or seasonal data — every point then looks out of control.