A City-Paid Consumer Advocate Wants to Secure Information About the Mean

Short Answer

A city-paid consumer advocate wants to secure information about the mean length, $\mu$ ,of coin-separated car wash cycles.A previous study reported the standard deviation of the length of car wash cycles to be 6 minutes.The advocate timed the wash cycle at 81 randomly selected car wash locations and the mean of the sample was 4.8 minutes.The 90 percent confidence interval estimate is 3.70 to 5.90 minutes.Interpret this interval.