According to a May 14, 2002, USA Snapshot, 81% of all drivers use their seat belts. You wish to conduct a survey in your city to determine what percent of the drivers use seat belts. Use the national figure of 81% for your initial estimate of p.

a. Find the sample size if you want your estimate to be within 0.02 with 90% confidence.

b. Find the sample size if you want your estimate to be within 0.04 with 90% confidence.

c. Find the sample size if you want your estimate to be within 0.02 with 98% confidence.

d. What effect does changing the maximum error have on the sample size? Explain.

e. What effect does changing the level of confidence have on the sample size? Explain.