Suppose that the specification limits for a production process are LSL = 0.02 and USL = 0.10, with the nominal specification being 0.06

What is the sigma level if the process standard deviation is 0.01

If the process is centered, what is the DPMO?

Suppose that there is a 0.015 process shift for the process. What is the DPMO?

what answers are which?

EXAMPLE 9.2 Calculating the Sigma Level Suppose that the specification limits for some process are LSL = 0.02 and USL = 0.10, with the nominal specification being 0.06. Find the sigma level if the process standard deviation is 0.01. Using equation (9.1): k x 0.01 = (0.10 -0.02)/2 or k=0.04/0.01 = 4 Therefore, this process operates at a 4-sigma level as long as it remains centered in the tolerance range (on 0.06) and the process mean does not drift by more than 1.5(0.01) = 0.015. The following Excel function can be used to calculate dpmo corresponding to the sigma level: =(1-NORM.DIST(sigma level, 1.5, 1, TRUE))*1000000 EXAMPLE 9.3 Calculating DPMO for a Sigma Level To verify the calculation of a six-sigma quality level using formula (9.2), we would find =(1-NORM.DIST(6, 1.5, 1, TRUE)) * 1000000 = 3.4 dpmo In Example 9.2, a four-sigma quality level corresponds to a dpmo value of =(1-NORM.DIST(4, 1.5, 1, TRUE)) * 1000000 = 6210 dpmo Using formula (9.2) we could tabulate dpmo for various sigma levels as shown in Table 9.2. You may use this table to estimate the value of dpmo for a given sigma level, or to estimate the sigma level for a given dpmo. We may also compute the exact sigma level for a given value of dpmo using the following Excel function: =NORM.S.INV(1 dpmo/1000000) + 1.5 (9.3)