18. Reconsider the paint-drying situation of Example 9.2, in which drying time for a test specimen is normally distributed with s  9. The hypotheses H0: m  75 versus Ha: m  75 are to be tested using a random sample of n  25 observations.

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

X x  30,960 x  30,960

b. If , what is the conclusion usinga.01?

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

2.88?

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

e. If the test procedure of part

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

f. If a level .01 test is used with n100, what is the probability of a type I error when m  76?