18. Reconsider the paint-drying situation of Example 8.2, in which drying time for a test specimen is normally distributed with
9. The hypotheses H0:
75 versus Ha:  75 are to be tested using a random sample of n
25 observations.

a. How many standard deviations (of X) below the null value is x
72.3?

b. If x

72.3, what is the conclusion using 
.01?

c. What is  for the test procedure that rejects H0 when z  2.88?

d. For the test procedure of part (c), what is
(70)?

e. If the test procedure of part

(c) is used, what n is necessary to ensure that
(70)
.01?

f. If a level .01 test is used with n
100, what is the probability of a type I error when
76?