n = z^2 (p*q)/ e^2

Using the formulas provided in your text, determine the approximate sample sizes for

each of the following cases, all with precision (allowable error) of + or - 5 percent:

a. Variability of 40%, confidence level of 95%

b. Variability of 55%, confidence level of 99%

c. Variability of 20%, confidence level of 90%

d. Unknown variability, confidence level of 95