Design of Experiments Guide • Prospective Sample Size and Power • Two Sample Proportions Calculator • Example of the Two Sample Proportions Calculator
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Example of the Two Sample Proportions Calculator
Suppose you are responsible for two silicon wafer assembly lines. Based on the knowledge from many runs, one of the assembly lines has a defect rate of 8% and the other line has a defect rate of 6%. You want to know the sample size necessary to have 80% power to conclude there is a difference in defect rates.
1.
Select DOE > Design Diagnostics > Sample Size and Power.
2.
Click Two Sample Proportions.
3.
Leave Alpha set at 0.05.
4.
Enter 0.08 for Proportion 1.
5.
Enter 0.06 for Proportion 2.
6.
Select a Two-Sided test.
7.
Enter 0 for Null Difference in Proportion.
8.
Leave Sample Size 1 and Sample Size 2 blank.
9.
Enter 0.8 for Power.
10.
Click Continue.
Figure 16.13 Difference between Two Proportions for a Two-Sided Test
The calculator shows that you should test a sample size of 2,554 wafers from each production line in order to detect a difference in defect rates.

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Help created on 10/11/2018