Refer to Exercise 13.17.
a. Using an indicator variable, fit a single model to the hops data for varieties Hallertau and Saaz.
b. Using your results from part (a), obtain separate prediction equations for varieties Hallertau and Saaz.
c. Interpret the values of the coefficients (βs) in the model.
d. Using your prediction equations in part (b), estimate the mean alpha acid percent-age when the atmospheric conditions are a mean temperature of 19° C and a mean sunshine of 6.5. How different are the two estimates?
e. Place 95% confidence intervals on your estimates.
In exercise

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Variety of Hops Fuggle Northerm Brewer Hallertau Field P S Field P S Field P S Field P T 12.1 16.8 4 55 6.5 4.4 68 16.7 4.4 2 5.8 174 58 2107170 622 5.3 171 58 24.9185 7.5 3 10.6 17.9 5.9 3 4.7 18.4 7.0 3 4.7 18.1 7.8 4 5.5 18.9 62410218.07.74 4.6 174 58 44.171 5.7 4.1 18.7 7.1 6 9. 21.3 6 64418.6 7.5 6 3.9 179 5.9 7 88 18.5 7.2 7 4.019.3 677 3.8 19.1 7.1 3.5 214 5.9 9 8 19.9 8.5 93221.4 6. 9 3.4 19.0 76 80 19.1 6.6 10 3.3 20.6 87 10 3.1 17.7 71 7.6 21.1 7.3 1 3.0 19.8 85 3.0 20.9 7.8 12 3.7 17.3 6.9124174 6.9 12 2.9 21.2 79 1 2.7 19.0 8.8 13 3.2 185 8613 5.8 19.2 8413 2.8 17.3 6.9 13 2.5 20 8.5 1 7.2 16.7 44 3 5.7 171 5.9 1 2 5 5.2 17.7 6.6 6 5.1 184 6.9 7 4.8 168 69 8 4.8 18.2 62 9 4.8 20.7 84 10 4.7 21.3 6210 11 4.3 21.2 7411 9.6 18.0 6.9 5 45 18.3 7.5 5 88 19.1 6,5 8 38 19.2 65 8 0