A researcher wishes to estimate, with 95% confidence, the population proportion of adults who think the
president of their country can control the price of gasoline. Her estimate must be accurate within 3% of the true proportion.
a) No preliminary estimate is available. Find the minimum sample size needed.
b) Find the minimum sample size needed, using a prior study that found that 40% of the respondents said they think their president can control the price of gasoline.
c) Compare the results from parts (a) and (b).