10.45 A certain pen has been designed so that true average writing lifetime under controlled conditions

(involving the use of a writing machine) is at least 10 hours. A random sample of 18 pens is selected, the writing lifetime of each is determined, and a normal probability plot of the resulting data supports the use of a one-sample t test. The relevant hypotheses are H0: m 5 10 versus Ha: m , 10.

a. If t 5 22.3 and a 5 .05 is selected, what conclusion is appropriate?

b. If t 5 21.83 and a 5 .01 is selected, what conclusion is appropriate?

c. If t 5 0.47, what conclusion is appropriate?