Fast ‘n Clean operates 12 laundromats on the east side of the city

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Fast ‘n Clean operates 12 laundromats on the east side of the city. All of Fast ‘n Clean’s clothes dryers have a label stating “20 minutes for $1.00.” You question the accuracy of the dryers’ clocks and decide to conduct an observational study. You randomly select 36 dryers in several different Fast ‘n Clean locations, put $1.00 in each and time the drying cycle. The sample mean drying time is 20 minutes and 25 seconds. The manufacturer of the dryer states that the standard deviation for 20-minute drying cycles is 1 minute.

a. Using the sample data and a = .05, test the validity of the label on the dryers. Apply the p-value and critical value approaches to conducting the two-tail hypothesis test.

b. Conduct the same two-tail hypothesis test, but this time use the confidence interval approach to hypothesis testing