Other things remaining the same, and assuming that X-bar is smaller than USL and larger than LSL, if the standard deviation (σ) of the process increases, process capability index (Cpk) of the process will
A) Stay the same
B) Will always increase
C) Will always decrease
D) Will sometimes increase

Question

Quizplus · Accepted Answer

Cpk is calculated as the minimum of (USL - X-bar)/(3σ) and (X-bar - LSL)/(3σ). If the standard deviation (σ) increases, the denominator of these fractions increases, leading to a decrease in the Cpk value.

Other Things Remaining the Same, and Assuming That X-Bar Is