Acertain 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 19 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: μ = 10 versus ha: μ < 10. (a) if t = −2.5 and α = 0.05 is selected, what conclusion is appropriate? reject fail to reject (b) if t = −1.83 and α = 0.01 is selected, what conclusion is appropriate? reject fail to reject (c) if t = 0.57, what conclusion is appropriate? reject fail to reject