The normal linear regression model Y =o+1X1+---+qu-+E is used to analyze a data set. and we have the following results: Model # X variables in model df SSRJDS 1 one 53 3.9? 3 2 X1 52 3.4960 3 X3 52 2.5762 4 X3 52 2.2154 5 X4 52 1.8??? 5 X1 . X2 51 2.2324 7 XI . X3 51 1.4073 8 X] , X4 51 1.3759 9 X2, X3 51 0.7431 10 X2. X4 51 1.3922 11 2(qu 51 1.2455 12 X1.X2.X3 50 0.1099 13 X1. X2. X4 50 1.3905 14 X1. X3. X4 50 1.115? 15 X2. X3. X4 50 0.4553 15 X1. X2. X3. X4 49' 0.1093 a. 1What. is the sample size of this data set? b. Excluding Model (16). which model would you recommend to use? Why? e. ls Model {13} a signicant model? C]. At. 10% level. should X1 and X2 be jointly added into Model (5)? e. 1it"l'hat is the proportion of (Explained variations dropped when X1 is dropped from Model (12)