Suppose a reference librarian selected a random sample of 30 customers before starting a new information retrieval system ...

Suppose a reference librarian selected a random sample of 30 customers before starting a new information retrieval system. The retrieval times in minutes are given below.
 

Information Retrieval
10 15 15 10 20 15 10 20 30 15 25 5 45 22 10 27 25 22 10 30 15 5 8 15 5 36 23 17 15 10
 

(a) Draw a histogram to summarize the retrieval times.
(b) Test for normality.
(c) Construct a 95% confident interval to estimate the mean retrieval time. Interpret the confidence interval.
(d) Does the sample provide sufficient evidence to conclude that mean retrieval time differs from 20 minutes? Use α = 0.05.
(e) Interpret the P-value of the test.