Case Study

Explain why the research team can be highly confident in their conclusion about sleep deprivation and cognitive performance, despite the individual methodological flaws of Study A and Study B. Specifically, describe how the concept of complementary strengths applies to this scenario.

Case context: A psychology research team is investigating the effects of sleep deprivation on cognitive performance. They review three studies: Study A is a highly controlled laboratory experiment with low external validity showing that sleep deprivation impairs memory. Study B is a correlational field study with high external validity but low internal validity showing the same impairment. Study C is a naturalistic observation with its own distinct methodological limitations that also finds the same relationship. All three studies converge on the same conclusion.

Question: Explain why the research team can be highly confident in their conclusion about sleep deprivation and cognitive performance, despite the individual methodological flaws of Study A and Study B. Specifically, describe how the concept of complementary strengths applies to this scenario.

Sample answer: The research team can be highly confident in their conclusion because the studies use diverse designs and contain different types of methodological flaws that all converge on the same finding. This allows the studies to provide complementary strengths: the low external validity of Study A (the true experiment) is balanced by the high external validity of Study B (the correlational study). Meanwhile, the low internal validity of Study B is balanced by the high control and internal validity of Study A. Because the weakness of one design is balanced by the strength of another, the flaws do not undermine the overall finding.

Key points:

  • The diverse designs and different methodological flaws converge on the same finding.
  • The weaknesses of one design are balanced by the strengths of another (complementary strengths).
  • The low external validity of the experiment (Study A) is balanced by the high external validity of the correlational study (Study B).
  • The low internal validity of the correlational study (Study B) is balanced by the high control of the experiment (Study A).

Rubric: The student must explain that converging findings from diverse designs with different flaws increase confidence. They must specifically identify how the low external validity of the true experiment is balanced by the high external validity of the correlational study, and how the low internal validity of the correlational study is balanced by the high control of the experiment, demonstrating comprehension of complementary strengths.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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