Case Study

Based on the provided context of the pretest-posttest nonequivalent groups design, explain why the researcher cannot conclude that the anti-drug program caused the change in attitudes. What does the equal change in both groups suggest about the influence of maturation or history?

Case context: A researcher evaluates an anti-drug program by administering a pretest on drug attitudes to students in School A (treatment group) and School B (nonequivalent control group). Students in School A complete the program, while students in School B do not. At posttest, students in both schools show an equally large, positive shift in their attitudes towards resisting drugs.

Question: Based on the provided context of the pretest-posttest nonequivalent groups design, explain why the researcher cannot conclude that the anti-drug program caused the change in attitudes. What does the equal change in both groups suggest about the influence of maturation or history?

Sample answer: The researcher cannot conclude that the program was effective because the students in the control school (School B), who did not receive the program, showed the same amount of attitude change as the treatment group (School A). This equal amount of change suggests that the attitude shift was caused by a confounding variable affecting both groups, such as natural maturation or a widespread historical event (e.g., a celebrity drug overdose or national drug-awareness news), rather than the anti-drug program itself.

Key points:

  • The treatment group did not show significantly more attitude change than the control group.
  • Because both groups changed equally, the program cannot be concluded to have caused the change.
  • The equal change points to a confound that affected both schools, such as maturation or a historical event.
  • The nonequivalent control group is necessary to identify when changes are due to general confounds rather than the treatment.

Rubric: The response should demonstrate comprehension by explaining that the lack of a significant difference in change between the treatment and control groups prevents a causal conclusion. It must also correctly link the equal change in both groups to confounds like maturation or history.

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Updated 2026-05-26

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Research Methods in Psychology - 4th American Edition @ KPU

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