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Understanding Replicability and External Validity

Dec 9, 2024

Chapter 14: Replicability, Generalization, and the Real World

Overview

  • Final chapter, summarizing and tying together previous discussions.
  • Divided into two major sections: Replicability and External Validity.
  • Importance: Applying learned concepts to real-world scenarios.

Replicability

Definition

  • Study’s ability to be repeated with similar conclusions.
  • Reliable results should be repeatable.

Types of Replication

  1. Direct Replication

    • Original study is repeated exactly to verify original effects.
    • Risks repeating internal/construct validity threats.

  2. Conceptual Replication

    • Same research question, different procedures.
    • Variables are operationalized differently.

  3. Replication Plus Extension

    • Original study replicated with additional variables.
    • Example: Note-taking study by Mueller and Oppenheimer.

Replication Crisis in Psychology

  • Many replication studies fail to find similar results.
  • Reasons for crisis:
    • Contextually sensitive effects.
    • Only one replication attempt may lead to missed true findings.
    • Problems with original studies (e.g., small sample size).

Solutions and Improvements

  • Larger sample sizes for original and replication studies.
  • Open Science Collaboration (OSC) and preregistration to improve transparency and reliability.

Meta-Analyses

Definition

  • Statistical analysis summarizing a body of literature.
  • Analyzes multiple studies to find overall consensus.

Strengths and Weaknesses

  • Strengths: Provides a comprehensive view.
  • Weaknesses: File drawer problem - unpublished null results may skew findings.

External Validity

Definition

  • Degree to which study findings generalize to the population of interest.
  • Important for study’s overall value.

Generalizing Findings

  • Population: Refers to a population of interest, not the entire world.
  • Sample Type: Probability sample for generalizability, convenience sample may not generalize.

Theory Testing vs Generalization Mode

  • Theory Testing Mode: Focus on internal validity, less on generalizability.
  • Generalization Mode: Use probability samples, focus on external validity.

Cultural Psychology

  • Emphasizes generalization mode.
  • Challenges reliance on "WEIRD" samples (Western, Educated, Industrialized, Rich, Democratic).

Ecological Validity

  • Study's setting relevance to real-world scenarios.
  • Field settings have high ecological validity.

Conclusion

  • Importance of study replicability and ecological validity for generalization.
  • Critical thinking and questioning are essential when evaluating scientific findings.
  • Note: For practical examples of replication issues and media portrayal, refer to John Oliver’s discussions on scientific studies.

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