An experiment analyzes imperfection rates for two processes used to fabricate silicon wafers for computer chips. For treatment A applied to 10 wafers, the numbers of imperfections are 8, 7, 6, 6, 3, 4, 7, 2, 3, 4. Treatment B applied to 10 other wafers has 9, 9, 8, 14, 8, 13, 11, 5, 7, 6 imperfections. Treat the counts as independent Poisson variates having means μA and μB. Consider the model logμ = α + βx, where x = 1 for treatment B and x = 0 for treatment A.

a. Show that β = logμB − logμA = log(μB/μA) and eβ = μb/μA.

b. Fit the model. Report the prediction equation and interpret ˆ β.

c. Test H0: μA = μB by conducting the Wald or likelihood-ratio test of H0: β = 0. Interpret.

d. Construct a 95% confidence interval for μB/μA. [Hint: Construct one for

β = log(μB/μA) and then exponentiate.]