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 hr. A random sample of 18 pens is selected,...

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 hr. A random sample of 18 pens is selected, the writing lifetime of each is determined, and a normal probability plot of the resulting data support the use of a one-sample t test. The relevant hypotheses are

H₀
:

= 10 versus H_a
:

, 10.

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

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

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