From: Stan Hilliard
Date: 1/31/2007
Time: 9:27:18 AM
If there were only two categories, the sample size depends on the population value of the percentage that you are estimating. The sample size to attain any chosen margin of error is a maximum at p'=50%. So what if you use 50% as your basis of calculation. That would assure that you have a large enough sample.
Or, you could use your current p' of the category closest to 50%. (Hispanic=32.8%)
If you want a program to do the calculations, our program "Audit Sample Planner" will lay out a table of sample sizes showing how n varies with p' and margin of error.
www.samplingplans.com/programasp.htm