During a period of one month, a random sample of 27 approved life insurance policies is selected, and the processing time, in days, is recorded:
73 19 16 64 28 28 31 90 60 56 31
56 31 56 22 18 45 48 17 17 17 91
92 63 50 51 69 16 17
(a) In the past, the mean processing time was 45days.At the 0.05 level of significant, is there evidence that the mean processing time has changed from 45days?
(b) What assumption about the population distribution is needed in order to conduct the t test in (a)?
(c) Use a box plot to evaluate the assumption made in (b)?
(d) Do you think that the assumption needed in order to conduct the t test in (a) is valid? Explain