A medical experiment compared the herb echinacea with a placebo for preventing colds. One response variable was "volume of nasal secretions" (if you have a cold, you blow your nose a lot). Take the average volume of nasal secretions in people without colds to be μ = 1. An increase to μ = 3 indicates a cold.

The significance level of a test of H0: μ = 4 versus Ha: μ > 4 is

a. The probability that the test rejects H0 when μ = 4 is true.

b. The probability that the test rejects H0 when μ = 9 is true.

c. The probability that the test fails to reject H0when μ = 4 is true.

d. The probability that the test fails to reject H0 when μ = 9 is true.