C.9. From Chapter 13
Comparing a Proportional Sample with the Population (95% Confidence)First, we must calculate a test value Zt. 
P = proportion of defects (or whatever) in the population (historical) p = proportion of defects (or same as above) in the sample |p – P|= absolute proportion difference (no minus sign in difference) n = sample size If Zt > 1.96, then we can say with a 95% confidence that the sample is different from the population. |
C.9.1. Use on Problem Type
Use this formula on proportional data when you want to test if a sample is significantly different from a population.
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