A researcher wishes to estimate, with 90%confidence, the population proportion of adults who are confident with their country’s banking system. His estimate must be accurate within 33%of the population 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 2525%of the respondents said they are confident with their country’s banking system.

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