we perform best subset, forward stepwise, and backward stepwise selection on a single data set. for each approach, we obtain p 1 models, containing 0, 1, 2,...,p predictors. explain your answers: (a) which of the three models with k predictors has the smallest training rss? (b) which of the three models with k predictors has the smallest test rss? (c) true or false: i. the predictors in the k-variable model identified by forward stepwise are a subset of the predictors in the (k 1)-variable model identified by forward stepwise selection. ii. the predictors in the k-variable model identified by backward stepwise are a subset of the predictors in the (k 1)- variable model identified by backward stepwise selection. iii. the predictors in the k-variable model identified by backward stepwise are a subset of the predictors in the (k 1)- variable model identified by forward stepwise selection. iv. the predictors in the k-variable model identified by forward stepwise are a subset of the predictors in the (k 1)-variable model identified by backward stepwise selection. v. the predictors in the k-variable model identified by best subset are a subset of the predictors in the (k 1)-variable model identified by best subset selection.
