Cp vs Cpk vs Pp vs Ppk: choose the right variation estimate
Worked capability examples explain centering, within-subgroup versus overall spread, and the checks needed before interpreting an index.
Control limits
Statistical boundaries calculated for a control chart under its chosen sampling model.
Control limits help detect variation inconsistent with the chart’s modeled common-cause behavior. They are not product acceptance limits. Chart selection, rational subgrouping, independence and distribution assumptions affect their usefulness. Read the SPC guide before interpreting a point beyond a limit or treating all points inside as proof of capability.
See also: Statistical process control (SPC) · Specification limits · Rational subgroup
Use the concept: Sample mean & standard deviation calculator · Cp, Cpk, Pp & Ppk calculator · Downtime log template
In depth
Statistical process control: control charts that catch drift early
Apply SPC where it works — control chart selection, rational subgrouping, capability indices, and the reaction plans that turn charts into control.
Takt time vs cycle time vs lead time: calculate the right clock
A worked shift example separates customer pace, observed process speed and end-to-end delivery time, with practical checks before changing the line.