Case Study

Explain why the research team's initial design introduces a confounding variable, and describe how implementing experimenter cross-condition testing would resolve this methodological issue.

Case context: A psychology research team is investigating the effects of a new study-aid app on students' test performance. They recruit 100 participants and divide them into a treatment group (using the app) and a control group (using standard paper flashcards). The team has two research assistants: Assistant A is outgoing and warm, and Assistant B is reserved and distant. In their initial design, the team assigns Assistant A to run all sessions for the treatment group, and Assistant B to run all sessions for the control group. A peer reviewer points out that this design introduces a confound, and suggests implementing experimenter cross-condition testing.

Question: Explain why the research team's initial design introduces a confounding variable, and describe how implementing experimenter cross-condition testing would resolve this methodological issue.

Sample answer: The initial design introduces a confound because Assistant A's warm demeanor is paired only with the treatment group, while Assistant B's cold demeanor is paired only with the control group. If the treatment group performs better, researchers cannot know if the app or the warm demeanor caused the effect. Implementing experimenter cross-condition testing would resolve this by having both Assistant A and Assistant B test participants in both the treatment and control groups, thereby spreading their unique interaction styles evenly across both conditions.

Key points:

  • Identify that assigning one assistant to one group creates a confound between the treatment/control variable and the experimenter demeanor.
  • Explain that any observed difference could be due to experimenter demeanor rather than the treatment.
  • Describe the cross-condition testing solution: both assistants must test participants in both the treatment and control groups.
  • Explain that this spreads the influence of each assistant's demeanor evenly across conditions.

Rubric: The response must correctly identify the confound (linking experimenter demeanor to a single condition) and explain how cross-condition testing resolves it by having all assistants run participants through all conditions to balance the influence.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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