How to use this calculator
Enter values in collection order. For a p chart, enter defective units for equally sized subgroups.
Formula and method
Individuals limits: x̄ ± 3MR̄/1.128. p-chart limits: p̄ ± 3√[p̄(1−p̄)/n], clipped to [0,1]. Cp/Cpk use within sigma; Pp/Ppk use overall SD.
Worked example
Measurements 9,10,11,10,9,10,11,10,9,10 have center 9.9; no points beyond limits.
Assumptions and supported scope
Individuals and fixed-n p charts only. One beyond-three-sigma rule. No X-bar/R, variable subgroup sizes, autocorrelation correction or normality validation. Capability assumes a stable roughly normal process.
Method references
Method and worked example checked against the calculator implementation. About our methods · Report a correction