A medical experiment compared zinc supplements with a placebo for reducing the duration of colds. Let μ denote the mean decrease, in days, in the duration of a cold. A decrease to μ = 1 is a practically important decrease. The significance level of a test of H0: μ = 0 versus Ha: μ > 0 is defined as a) the probability that the test fails to reject H0 when μ = 1 is true.
b) the probability that the test rejects H0 when μ = 0 is true.
c) the probability that the test rejects H0 when μ = 1 is true.