a.-d. Repeat Problem 3, using REACTIM2 as the dependent variable and referring to the accompanying computer output.
In problem 3
a. Observe the cross-tabulation of AGEGROUP and PPM_CO in the accompanying SAS PROC FREQ computer output. Why might this be called a nearly orthogonal two-way design? Any missing data were due to technical problems unrelated to the response variable or treatments.
b. Using dummy variables coded -1 and 1 for AGEGROUP = young and old, respectively, and coded — 1 and 1 for PPM_CO = 0 and 100, respectively, define dummy variables and a corresponding multiple regression model for a two-way ANOVA.
c. Use an appropriate computer program to fit the regression model in part (b). Report appropriate tests of the AGEGROUP × PPM_CO interaction and tests of their main effects in an appropriate summary source table.
d. SAS's PROC GLM procedure automatically codes dummy variables (and properly treats unequal sample sizes). The accompanying PROC GLM computer output shows the two-way ANOVA results for this problem. Complete the F statistics in the ANOVA table, and report the results of the same tests as in part (c). Compare the results to those in part (c), and explain any differences.