A study compared dry matter intake (dmi) in mature cows (C) and heifers (H) receiving no treatment (control), treatment A, or treatment B. The two factors are type of animal and treatment. Each factor combination has eight animals. The above plot of the means, which is derived from a two-factor analysis of variance, is called:
A)an interaction plot.
B)a parallel means plot.
C)a nonparallel means plot.
D)a crossover plot.

Question

A study compared dry matter intake (dmi) in mature cows (C) and heifers (H) receiving no treatment (control), treatment A, or treatment B. The two factors are type of animal and treatment. Each factor combination has eight animals.  The above plot of the means, which is derived from a two-factor analysis of variance, is called:
A)an interaction plot. 
B)a parallel means plot. 
C)a nonparallel means plot. 
D)a crossover plot.

Quizplus · Accepted Answer

The plot of means shown in the question is an interaction plot, which displays the interaction effect between the two factors (type of animal and treatment) on the dry matter intake. The presence of an interaction suggests that the effect of one factor on the outcome variable depends on the levels of the other factor. In other words, the effect of treatment A versus B on dry matter intake differs depending on whether the animal is a cow or a heifer. Therefore, the best choice is (A), an interaction plot.

A Study Compared Dry Matter Intake (Dmi) in Mature Cows