Which graph shows means of two or more independent variables with means at different levels of another variable, often displaying lines or bars to illustrate interactions?

• A. Scatter plot of group means
• B. Line graph of group means
• C. Bar chart of group means
• D. Interaction graph

Answer: (D)

In experiments with two or more factors, you look for interactions—scenarios where the effect of one factor depends on the level of another. The graph that best shows this is an interaction graph. It plots the mean of the dependent variable for every combination of factor levels and typically uses separate lines (one for each level of a factor) or bars to compare across the other factor. If the lines are not parallel or they cross, that indicates an interaction: the impact of one factor changes across levels of the other. Scatter plots of group means don’t specifically depict factorial interactions, and while a line graph or bar chart can display means, the term “interaction graph” explicitly conveys the goal of illustrating how factors interact.