A researcher wishes toestimate, with 90

90% 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 4

4% of the true proportion.

a) No preliminary estimate is available. Find the minimum sample size needed.

b) Find the minimum sample sizeneeded, using a prior study that found that 28

28% of the respondents said they think their president can control the price of gasoline.

c) Compare the results from parts(a) and(b).