Case Study

Based on the concept of maturation as a threat to internal validity, diagnose why the researcher's conclusion might be flawed and explain what alternative factor could account for the observed differences.

Case context: A researcher conducts a year-long intervention designed to improve logical reasoning skills in middle school children. The children complete a reasoning pretest in September and a posttest the following September. The results show a significant increase in reasoning scores, leading the researcher to conclude that the intervention was highly effective.

Question: Based on the concept of maturation as a threat to internal validity, diagnose why the researcher's conclusion might be flawed and explain what alternative factor could account for the observed differences.

Sample answer: The researcher's conclusion might be flawed because the children could have naturally become better reasoners over the course of the year-long intervention, simply as a result of growing older and learning. This natural developmental change (maturation), rather than the intervention itself, could be the actual cause of the increased reasoning scores on the posttest.

Key points:

  • The study's conclusion is vulnerable to a maturation threat.
  • Children naturally become better reasoners over the course of a year-long period.
  • The observed difference in the dependent variable may be due to growing older or learning.
  • These ongoing changes might be misconstrued as an effect of the experimental treatment.

Rubric: Full credit is awarded for diagnosing maturation as the specific threat to internal validity and explaining how natural developmental changes over the year could cause the increased reasoning scores rather than the intervention.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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