6. As part of an annual review of its accounts, a discount brokerage selects a randomsample of 36 customers. Their accounts are reviewed for total account valuation, whichshowed a mean of $32,000, with a sample standard deviation of $8,200.

a. Develop a 90 percent confidence interval for the mean account valuation.

b. What is the margin of error for part a?

c. List the factors that determine the margin of error.