You wk for a consumer advocate agency and want to find the mean repair cost of a washing machine. As part of your study, you randomly select 45 repair costs and find the mean to be $115. The sample standard deviation is $16.40.
a. construct 90% of the mean confidence interval for the population of mean repair cost
b.the 90% interval confidence is _____ , ______ (Round to two decimal places as needed).