Free SPC Control Chart Generator
Paste your data, see control charts with Nelson rules and Cpk analysis instantly. Your data never leaves your browser — all calculations run locally.
Paste your data, see control charts with Nelson rules and Cpk analysis instantly. Your data never leaves your browser — all calculations run locally.
125 data points in 25 subgroups of 5 — chart type: X-bar R (recommended)
Recommended: your data has 5 columns per row, matching subgroup size 5
Two of three consecutive points beyond 2-sigma on the same side
Increased process variation near the control limits — may indicate an intermittent special cause such as loose fixturing, inconsistent material, or periodic environmental disturbance.
Four of five consecutive points beyond 1-sigma on the same side
A process shift developing — the mean is drifting toward a control limit. Check for gradual changes in materials, settings, or environmental conditions.
Your process shows special cause variation. 2 pattern violations were detected across 25 subgroups. The process is not in statistical control — assignable causes should be identified and addressed. Enter specification limits to assess process capability.
This assessment is based on statistical analysis of the provided data. It does not replace domain expertise or process knowledge. Always verify findings with process owners before taking corrective action.
Data does not follow a normal distribution. Capability indices assume normality and may be unreliable. Consider investigating subgroups for outliers, check for process shifts using the control chart, or evaluate whether a data transformation (Box-Cox) may be appropriate.
Enter specification limits (USL / LSL) above to see capability indices (Cp, Cpk, Pp, Ppk).
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