Measurements were taken for the workstation that tests the test machines; the data is:
Mean 118.45
Standard Dev 0.35
Lower Spec 117.56
Upper Spec
119.73
Determine the capability index. (Keep four decimal places in your answer)
Expert Answer
Mean = 118.45
Standard deviation = 0.35
Lower specification limit (LSL) = 117.56
Upper specification limit (USL) = 119.73
Cpl = (Mean – LSL) / (3 x standard deviation)
= (118.45 – 117.56) / (3 x 0.35)
= 0.89 / 1.05
= 0.8476
Cpu = (USL – Mean) / (3 x standard deviation)
= (119.73 – 118.45) / (3 x 0.35)
= 1.28/1.05
= 1.2190
Capability index = Minimum of (Cpl, Cpu)
= Minimum of (0.8476,1.2190)
= 0.8476