Explain why the researcher cannot conclude that the anti-drug program caused the change in attitudes, and explain what the equal change in both groups suggests about the threat of maturation or history to the study's internal validity.
Case context: A researcher evaluates a new school-based anti-drug program using a pretest-posttest nonequivalent groups design. Students in School A (treatment group) complete a pretest on drug attitudes, participate in the program, and take a posttest. Students in School B (nonequivalent control group) complete the same pretest and posttest but do not participate in the program. At the posttest, students in both schools exhibit an identical, positive shift in their attitudes toward resisting drugs.
Question: Explain why the researcher cannot conclude that the anti-drug program caused the change in attitudes, and explain what the equal change in both groups suggests about the threat of maturation or history to the study's internal validity.
Sample answer: The researcher cannot conclude that the anti-drug program caused the change in attitudes because the control group (School B), which did not receive the treatment, showed the same positive shift as the treatment group (School A). This equal change suggests that the shift was not caused by the program but by a confounding variable. Specifically, it suggests the influence of either maturation (natural developmental changes in the students' reasoning and attitudes over time) or history (an external event, such as a widespread media campaign about drug abuse, that occurred during the study and affected students in both schools).
Key points:
- Attributing the change to the program is invalid because the control group showed the same change.
- Identifies maturation as a threat, where natural student development over time caused the attitude shift.
- Identifies history as a threat, where a shared external event during the study period caused the attitude shift.
Rubric: Answers should be graded based on whether the student: 1) Explains that the identical change in both groups makes it impossible to attribute the effect to the program. 2) Explains how maturation (developmental progression over time) could account for the equal change. 3) Explains how history (external events occurring during the study) could account for the equal change.
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Research Methods in Psychology - 4th American Edition @ KPU
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When evaluating an anti-drug program by comparing one school that receives the program to a similar school that does not, researchers measure student attitudes both before and after the program. What is the primary reason for comparing the amount of 'pretest-to-posttest change' between the two schools, rather than simply comparing their final scores?
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Explain why the researcher cannot conclude that the anti-drug program caused the change in attitudes, and explain what the equal change in both groups suggests about the threat of maturation or history to the study's internal validity.