The true average diameter of ball bearings of a certain type is supposed to be 0.5 in. A one-sample t-test will be carried out to see whether this is the case. What conclusion is appropriate in each of the following situations?
(a) n = 13, t = 1.6, α = 0.05.
(b) n = 13, t = -1.6, α = 0.05.
(c) n = 25, t = -2.6, α = 0.01.
(d) n = 25, t = -3.9, α = 0.01.