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

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