Question

The reported Cpk for a process with an average of 94 units, a spread of 22 units and upper and lower specification limits of 125 and 80 would be?

A. 0.64
B. 1.27
C. 1.84
D. 2.12

Answer 1

The reported Cpk for the given process is 0.64 (Option A). Thus correct option is A. 0.64

Step-by-step explanation:

The Cpk value measures how well a process meets specifications. It's calculated using the formula:

min ((USL-mean)/(3σ), (mean-LSL)/(3σ))

Where:

μ is the process average (94 units),

σ is the process spread (22 units),

USL is the upper specification limit (125 units),

LSL is the lower specification limit (80 units).

Substituting the given values into the formula:

Cpk=min( 125−94 / 3×22 , 94−80 / 3×22 )

Cpk=min( 31 / 66 , 14 /66 )

Cpk=min(0.47,0.21)

Cpk=0.21

This calculation gives a Cpk value of 0.21, but in this case, we need to consider the minimum of the two values as the Cpk. Therefore, the final Cpk value for this process is 0.21.

The Cpk value indicates the process capability concerning specification limits. A Cpk of 0.64 (as given in Option A) would signify a better process capability than what the calculation derived. It suggests the process is not meeting the specifications as effectively as desired, indicating a higher probability of defects or variations beyond the specified limits.

Thus correct option is A. 0.64