A 10-year study conducted by the American Heart Association provided data on how age, blood pressure, and smoking relate to the risk of strokes. Data from a portion of this study follow. Risk is interpreted as the probability (times 100) that a person will have a stroke over the next 10-year period. For the smoker variable, 1 indicates a smoker and 0 indicates a nonsmoker.

Risk amp;Age amp;Blood Pressure amp;Smoker

24 amp;57 amp;152 amp;0

13 amp;67 amp;163 amp;0

56 amp;58 amp;155 amp;0

28 amp;86 amp;177 amp;1

51 amp;59 amp;196 amp;0

18 amp;76 amp;189 amp;1

31 amp;56 amp;155 amp;1

37 amp;78 amp;120 amp;0

15 amp;80 amp;135 amp;1

22 amp;78 amp;98 amp;0

36 amp;71 amp;152 amp;0

15 amp;70 amp;173 amp;1

48 amp;67 amp;135 amp;1

15 amp;77 amp;209 amp;1

36 amp;60 amp;199 amp;0

8 amp;82 amp;119 amp;1

34 amp;66 amp;166 amp;0

3 amp;80 amp;125 amp;1

37 amp;62 amp;117 amp;0

Required:

a. Develop an estimated regression equation that can be used to predict the risk of stroke given the age and blood-pressure level.

b. Consider adding two independent variables to the model developed in part (a), one for the interaction between age and blood-pressure level and the other for whether the person is a smoker. Develop an estimated regression equation using these four independent

variables.

c. At a .05 level of significance, test to see whether the addition of the interaction term and the smoker variable contribute significantly to the estimated regression equation developed in part (a).