A marketing analyst assessed the effect of web page design (A, B, or C) on customers' intent to purchase an expensive product. The focus group was divided randomly into three sub-groups, each of…

Question

Options

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

• A
  60% (12)
• B
  20% (4)
• C
  10% (2)
• D
  10% (2)

Explanation

Graph A must show non-parallel lines where the high-income group (III) displays a pronounced difference in purchase intent across the three webpage designs, while the low- and medium-income lines remain relatively flat or close together - this pattern is the visual signature of a significant interaction where one subgroup drives the effect.

Why the distractors are wrong:

• Graph B likely shows parallel lines across all income groups, indicating a main effect of webpage design with no interaction (all income levels respond similarly).
• Graph C likely shows non-parallel lines, but the divergence is driven by a low- or medium-income group rather than the high-income group, contradicting the analyst's specific claim.
• Graph D likely shows either no effect at all, or a main effect of income alone (lines shift up/down uniformly) without interaction.

Memory tip: For interaction questions, ask yourself two things: (1) Are the lines non-parallel? (interaction present) and (2) Which group causes the crossing or divergence? The correct graph must satisfy both the "significant interaction" claim and the "mainly high income" claim simultaneously - rule out any graph that satisfies only one condition.

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