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. Click on the datafile logo to reference the data. Enter negative values as negative, if necessary. Use the best subset regression procedure to predict risk of stroke. Which independent variable provides the best regression model if only one independent variable is in the model?