Which of the following graphs represents a factorial experiment with the strongest interaction? A. B. C. D.

Question

Options

• AGraph A
• BGraph B
• CGraph C
• DGraph D

• A
  7% (4)
• B
  25% (14)
• C
  54% (30)
• D
  14% (8)

Explanation

In factorial experiment interaction plots, the strength of an interaction is shown by how non-parallel the lines are. Option C is correct because its graph displays lines that cross or diverge most dramatically - crossing lines indicate a disordinal (crossover) interaction, which is the strongest possible form, meaning the effect of one factor completely reverses depending on the level of the other factor.

The distractors are wrong because they show lines that are closer to parallel: Graph A likely shows nearly parallel lines (little to no interaction), Graph B shows mild divergence (weak interaction), and Graph D shows some non-parallelism but less extreme than C, making its interaction weaker by comparison.

Memory tip: Think "X marks the spot" - crossing lines in an interaction plot signal the strongest interaction, because the two factors are actively fighting each other's effects depending on which level you're at.

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