Which of the following statements about a two-way analysis of variance model is/are TRUE? a. The population of interest is classified according to two categorical variables, or factors. b. An experiment involving the simultaneous use of two factors offers advantages over two one-way experiments with respect to such matters as efficiency and reduction of residual variation. c. The two-way type of experiment requires twice as many experimental observations as would be required in two one-way experiments of the same factors. d. An experiment involving the simultaneous study of two factors allows for the investigation of interactions between the factors. e. Only A, B, and D are true.