LESSON 14 - THREATS TO INTERNAL AND EXTERNAL VALIDITY OF EXPERIMENTAL DESIGNS

LESSON 14 - THREATS TO INTERNAL AND EXTERNAL VALIDITY OF EXPERIMENTAL DESIGNS

by Prof. Lydia Wambugu

Humanities, Social Sciences & Thought Science — General & History GPSResearch methodsGPSDQuantitative research methods
🎙 Prof. Lydia Wambugu 👥 29K 📅 April 21, 2021 ⏱ 24 min 👁 7K 📄 tutorial 🧭 2026-08-17
Available in: English (current) Français

Keywords

internal validityexternal validityexperimental designthreatscausality

Summary

This lesson, part of a research methods course, focuses on threats to internal and external validity in experimental designs. The instructor, Prof. Lydia Wambugu, begins by emphasizing that experimental designs are unique in establishing causality (X causes Y). To be confident in this conclusion, researchers must control extraneous variables and avoid spurious correlations. The lesson then defines internal validity as the extent to which a study establishes a trustworthy cause-and-effect relationship between independent and dependent variables. Threats to internal validity are presented in a table, each with an example and mitigation strategy: history, testing, maturation, instrumentation, selection bias, experimental mortality, statistical regression, diffusion of treatment, compensation/resentful demoralization, and compensatory rivalry. Next, external validity is defined as the generalizability of findings to other settings, people, and times. Threats to external validity include interaction effects of selection, setting, history, reactive effects of testing, experimenter effects, and the Hawthorne effect. The lesson concludes with general strategies to minimize threats: randomization, double-blind procedures, researcher neutrality, prolonging time between treatments, and using placebo groups. The instructor encourages questions and subscription.

175 words

Critical Evaluation

Value of the Information & Strength of the Argument

The lesson provides a comprehensive and systematic overview of threats to internal and external validity, which is valuable for students and researchers in social sciences. The instructor uses clear examples (e.g., behavior change program) to illustrate each threat, making the concepts accessible. The argumentation is logically structured, moving from definitions to specific threats and then to mitigation strategies. However, the lesson lacks depth in discussing the philosophical underpinnings of validity and does not address contemporary debates or advanced topics like quasi-experimental designs. The reliance on a single example may limit the generalizability of the explanations.

Scientific Rigor, Source Quality, Title Accuracy

The lesson demonstrates a solid understanding of classic research methodology concepts, but it does not cite specific academic sources or empirical studies. The instructor relies on established textbook knowledge, which is generally reliable but not up-to-date with recent methodological innovations. The title accurately reflects the content, and the lesson is well-organized. The absence of citations to external literature is a limitation for viewers seeking to verify or expand on the information. The description provides links to the instructor’s course and social media, but these are not academic sources.

198 words

Title / Content Match

The title accurately reflects the content, which focuses exclusively on threats to internal and external validity in experimental designs.

Quality & Reliability

7/10

The lesson provides a clear and structured overview of threats to internal and external validity in experimental designs, with practical examples and mitigation strategies. It is based on established research methodology concepts, but lacks citations to specific sources and does not engage with recent methodological debates.

Key Moments

Markers derived by PSI from the transcript: the creator did not define chapters.

Cited Sources

  • Research Methods Course — Full course mentioned in the video description
  • YouTube Channel — Channel subscription link in description
  • LinkedIn — Instructor's LinkedIn profile
  • Facebook — Instructor's Facebook page
  • Instagram — Instructor's Instagram page
  • Live Chat — WhatsApp live chat link

Concurring Sources

Dissenting Sources

  • None — No conflicting sources were identified.

Contribution & Novelties

This lesson provides a clear and structured introduction to threats to internal and external validity, which is a fundamental topic in experimental research. Its originality lies in its pedagogical approach, using a consistent example to illustrate each threat and mitigation strategy. However, it does not offer new insights beyond standard textbook material.

Pour aller plus loin :

113 words

Radar Profile

The radar profile shows high scores in quantity of information and fiabilite, with moderate scores in quality and technical level. This indicates a comprehensive but not deeply technical presentation, suitable for an introductory audience.

Reliability 7/10

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