2.22. The time to repair an electronic instrument is a normally distributed random variable measured in hours. The repair times for 16 such instruments chosen at random are as follows:

Hours 159 280 101 212 224 379 179 264 222 362 168 250 149 260 485 170

(a) You wish to know if the mean repair time exceeds 225 hours. Set up appropriate hypotheses for investigating this issue.

(b) Test the hypotheses you formulated in part (a). What are your conclusions? Use ( $ 0.05.

(c) Find the P-value for the test.

(d) Construct a 95 percent confidence interval on mean repair time.