Q1 - Process capability indices using subgroup averages and standard deviations A quality engineer collected process data for five subgroups with each subgroup consisting of four samples (n=4). The averages and standard deviations of samples in each subgroup are summarized in Table 1 below. The upper specification limit (USL) of the process is 13.05 and the lower specification limit (LSL) is 12.95 Table 1. Subgroup Data Subgroup 1 2 3 5 Average X 13.01 12.97 13.00 12.99 12.98 Standard deviations 0.04 0.03 0.04 (1-1) Calculate the average X of subgroup averages X. Answer X (average of subgroup averages X) 4 0.02 0.02 (1-2) Calculate the average 5 of subgroup standard deviation s. 5 (average of subgroup standard deviations s) Answer (1-3) Calculate the estimate of population standard deviation Answer a (estimate of population standard deviation) 1-3 (1-4) Calculate the process capability index Cy. Answer C