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Result
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Uses standard X-bar/R chart constants A2, D3 and D4 for subgroup sizes 2–10. Use rational subgroups and a stable process baseline.
How to use this calculator
What to enter
Enter or select the following as requested: Subgroup size; Subgroup means; Subgroup ranges. Follow the units, valid ranges, examples, and options displayed beside each field.
What the result means
The X-bar chart tracks subgroup averages, while the R chart tracks within-subgroup variation. Use consistent subgroup sizes and investigate unusual signals before concluding that the process is stable.
When to use it
Use this to analyze process quality or plan a quality-improvement study. Verify data collection and statistical assumptions before changing a process or reporting formal capability results.