A researcher wishes to estimate the proportion of eligible voters who will vote for a particular candidate in the upcoming election:
a) How large should the sample size be so that a 85% confidence intervalfor the population proportion has a margin of error of 0.05. Assume that a preliminary sample suggests the proportion is 0.65.
b) Assuming that the results of a preliminary surveyare not available. What is the most conservative estimate of the sample size that would limit the margin of error to within 0.05 of the population proportion for an 95% confidence interval?
The required sample sizes are calculated.