Cp Cpk Out Of Tolerance. Process capability index cpk. Cp indicates the spread of variation present in a process.
Cp et nt usl lsl 6σ. The first capability ratio cp is defined as the ratio of the engineering tolerance usl lsl to the natural tolerance 3 s to 3 s. Where s is the process standard deviation estimated from a range control chart.
In a quality control context ppm stands for the number of parts per million cf.
Process capability index cpk. Cpk 1 00 means that 2 700 ppm 0 27 of the manufactured parts are out of tolerance while cpk 1 33 means that 63 ppm 0 0063 are rejects. Percent that lie outside the tolerance limits. This is the capability index which accounts for centering of process and is defined as the minimum of cpk upper and cpk lower.
