1. Variable Selection 1 Chapter 8 Variable Selection Terry Dielman Applied Regression Analysis: A Second Course in Business and Economic Statistics, fourth edition

2. 2 POP QUIZ #11 [2.5 points]

3. 3 POP QUIZ #11 1. Which one of the following is NOT a model selection procedure? A.Stepwise Regression B.Forward Selection C.Backwards Selection D.Backwards Elimination

4. 4 POP QUIZ #11 2.Some model selection algorithms have the ability to use a researcher's knowledge about the business or economic situation being analyzed: A.True B.False

5. 5 POP QUIZ #11 3. The recommended c p value is: A.Near k + 1, where k is the # of predictors B.Near n + 1, where n is the # of observations C.Near p + 1, where p is the # of model parameters D.Near p – 1, where p is the # of model parameters

6. 6 4. Based on c p, which model is most appropriate? A.The one using {Adv} as the only predictor B.The one using {Adv,Mktshr} as the predictors C.The one using {Adv,Bonus,Mktshr} D.The one using {Adv,Bonus,Mktshr,Compet} M C B K O O T M A N S P D U H E Vars R-Sq R-Sq(adj) C-p S V S R T 1 81.1 80.2 5.9 101.42 X 1 32.3 29.3 75.2 191.76 X 2 85.5 84.2 1.6 90.749 X X 2 81.2 79.5 7.7 103.23 X X 3 85.8 83.8 3.1 91.751 X X X 3 85.7 83.6 3.3 92.255 X X X 4 85.9 83.1 5.0 93.770 X X X X POP QUIZ #11

7. 7 5.Which shortcoming of the Backwards procedure has been addressed with the introduction of the Stepwise Regression procedure? A.Variables that get eliminated are never considered again B.Variables currently in, are never dropped C.Variables entering stay in, even if they lose significance D.Some variables never enter the model

8. 8 Answers! √

9. 9 POP QUIZ #11 1. Which one of the following is NOT a model selection procedure? A.Stepwise Regression B.Forward Selection C.Backwards Selection D.Backwards Elimination √

10. 10 POP QUIZ #11 2.Some model selection algorithms have the ability to use a researcher's knowledge about the business or economic situation being analyzed: A.True B.False √

11. 11 POP QUIZ #11 3. The recommended c p value is: A.Near k + 1, where k is the # of predictors B.Near n + 1, where n is the # of observations C.Near p + 1, where p is the # of model parameters D.Near p – 1, where p is the # of model parameters √

12. 12 4. Based on c p, which model is most appropriate? A.The one using {Adv} as the only predictor B.The one using {Adv,Mktshr} as the predictors C.The one using {Adv,Bonus,Mktshr} D.The one using {Adv,Bonus,Mktshr,Compet} M C B K O O T M A N S P D U H E Vars R-Sq R-Sq(adj) C-p S V S R T 1 81.1 80.2 5.9 101.42 X 1 32.3 29.3 75.2 191.76 X 2 85.5 84.2 1.6 90.749 X X 2 81.2 79.5 7.7 103.23 X X 3 85.8 83.8 3.1 91.751 X X X 3 85.7 83.6 3.3 92.255 X X X 4 85.9 83.1 5.0 93.770 X X X X POP QUIZ #11 √

13. 13 POP QUIZ #11 5.Which shortcoming of the Backwards procedure has been addressed with the introduction of the Stepwise Regression procedure? A.Variables that get eliminated are never considered again B.Variables currently in, are never dropped C.Variables entering stay in, even if they lose significance D.Some variables never enter the model √