The upper and lower specification limits for a component are 0.150 cm.and 0.120 cm.,respectively.The process standard deviation is 0.003 cm.and the process average is 0.138 cm.What conclusion can be drawn?
A) The process is capable.
B) The process average is out of statistical control.
C) The process is not capable.
D) The specifications should be changed to 0.141 and 0.135, respectively.

Question

Quizplus · Accepted Answer

In order to determine if the process is capable or not, we need to calculate the process capability index (Cpk). Cpk is calculated as min[(USL-μ)/(3σ), (μ-LSL)/(3σ)], where USL is the upper specification limit, LSL is the lower specification limit, μ is the process average, and σ is the process standard deviation.

Cpk = min[(0.150-0.138)/(3*0.003), (0.138-0.120)/(3*0.003)] = min[4, 6] = 4

Since Cpk is greater than 1, we can conclude that the process is capable of meeting the specification limits. Therefore, the answer is choice A.

The Upper and Lower Specification Limits for a Component Are