A researcher wishes to? estimate, with 99?% confidence, the population proportion of adults who are confident with their? country's banking system. His estimate must be accurate within 4?% 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 26?% of the respondents said they are confident with their? country's banking system.
?(c) Compare the results from parts ?(a) and ?(b).