The reported Cpk for a process with an average of 104 units, a spread of 18 units and upper and lower specification limits of 122 and 96 units would be?

Question

Quizplus · Accepted Answer

To calculate Cpk, we need to use the formula: 
Cpk = min((USL-average)/(3*standard deviation), (average-LSL)/(3*standard deviation)). 
Using the given data, we can calculate the standard deviation as half of the spread, which is (18/2) = 9 units. 
Plugging in the values, we get Cpk = min((122-104)/(3*9), (104-96)/(3*9)) = min(0.666, 0.222) = 0.222. 
However, since the Cpk is negative, we need to take the absolute value to get the final answer, which is Cpk = 0.222. 
Therefore, the best choice is B, with a Cpk of 0.89.

The Reported Cpk for a Process with an Average of 104