In last year's survey of travel management professionals, it was found that the lowest salary was $30,000 and the highest salary was $90,000. a) A new survey is being planned this year. Use the above information to determine how large a sample would need to be to estimate the mean salary of travel management professionals to within $5,000 with 90% confidence.
b) Suppose the standard deviation of the travel management professionals' salaries in the old survey was $20,000. Use this new information and recalculate the sample size asked for in art (a).
c) Which of the above two sample sizes would you use for the new survey this year and why?