A researcher wishes to estimate, with 95% confidence, the population proportion of adults who are confident with their country's banking system. His estimate must be accurate within 2% 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 22% of the respondents said they are confident with their country's banking system.

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

(a) What is the minimum sample size needed assuming that no prior information is available? nequals nothing (Round up to the nearest whole number as needed.)

(b) What is the minimum sample size needed using a prior study that found that 22% of the respondents said they are confident with their country's banking system? nequals nothing (Round up to the nearest whole number as needed.)