Data Set 13-7: A political scientist reported a study on attitudes toward increasing military expenditures. The attitudes of four groups were reported: US Army officers, corporate managers, public school teachers, and assembly-line workers. Within each of the categories, those under age 35 were tabulated separately from those over 35. A factorial ANOVA on the data produced a significant interaction; the main effect for age was not significant.
-The degrees of freedom for the interaction mean square in Data Set 13-7 is
A) 1
B) 3
C) 6

Question

Quizplus · Accepted Answer

The degrees of freedom for the interaction in a factorial ANOVA are calculated by multiplying the degrees of freedom of the factors involved in the interaction. Here, we have two factors: type of occupation (4 groups) and age (2 groups). The degrees of freedom for occupation are 4 - 1 = 3, and for age, they are 2 - 1 = 1. Thus, the degrees of freedom for the interaction are 3 * 1 = 3.

Data Set 13-7: a Political Scientist Reported a Study on Attitudes