In the accompanying table, we give the smallest SSE for each number of predictors k (k
1, 2, 3, 4) for a regression problem in which y
cumulative heat of hardening in cement, x1
% tricalcium aluminate, x2
% tricalcium silicate, x3
% aluminum ferrate, and x4
% dicalcium silicate.

Number of Predictors k Predictor(s) SSE 1 x4 880.85 2 x1, x2 58.01 3 x1, x2, x3 49.20 4 x1, x2, x3, x4 47.86 In addition, n
13, and SST
2715.76.

a. Use the criteria discussed in the text to recommend the use of a particular regression model.

b. Would forward selection result in the best two-predictor model? Explain.