Use the OC Curve platform to estimate the probability of identifying a process shift with the first sample collected after the shift.
1. Select Analyze > > Quality and Process > OC Curves.
2. Select XBar Shewhart Chart.
3. Click OK.
4. Set the control limits to -1.34 and 1.34. These are 3 sigma limits for s = 1 and n = 5 (3 times 1 divided by the square root of 5).
5. Leave Sigma set to 1 and the sample size at 5.
6. Set Shift to 2.
Figure 18.1 OC Curve Example
The Y axis is the Beta risk, or the probability of not detecting a shift. The probability of detecting a shift of size 2s with a sample of size 5 is 1 - 0.07 = 0.93.