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Experimental Design: True, Quasi- and Pre-Experimental

👥 Sociology By CampusDown Wiki Editorial Team Last updated
Quick answer: Experimental designs test cause and effect by manipulating a treatment and comparing with a control group; they are classed as true, quasi- or pre-experimental by whether random assignment and controls are used.
Contents
  1. 1. Conditions for causality
  2. 2. Pre-experimental designs
  3. 3. True experimental designs
  4. 4. Quasi-experimental designs
  5. 5. Validity
  6. 6. References

Conditions for causality

A cause must precede its effect, the variables must covary, and rival explanations must be ruled out. Experiments use control groups and random assignment to meet the third condition, a core idea of quantitative research.

Pre-experimental designs

  • One-shot case study: X O.
  • One-group pretest-posttest: O X O; cannot rule out history or maturation.
  • Static-group comparison: posttest-only comparison without random assignment.

True experimental designs

  • Pretest-posttest control group: R O X O / R O O.
  • Posttest-only control group: R X O / R O, avoiding testing effects.
  • Solomon four-group: combines both to separate pretest and treatment effects.
  • Factorial designs test several factors and their interactions.

Quasi-experimental designs

Used when randomisation is impractical: nonequivalent control group (O X O / O O), interrupted time series (O O O X O O O) and control-series designs, common in programme evaluation.

Validity

Stronger designs better control threats to internal validity such as history, maturation, testing, instrumentation, regression, selection and attrition, though artificial settings can reduce external validity. Human experiments also need ethical review.

References

  1. Campbell, D. T., & Stanley, J. C. (1963). Experimental and Quasi-Experimental Designs for Research. Rand McNally.
  2. Shadish, W. R., Cook, T. D., & Campbell, D. T. (2002). Experimental and Quasi-Experimental Designs for Generalized Causal Inference. Houghton Mifflin.
  3. Rubin, A., & Babbie, E. R. (2017). Research Methods for Social Work (9th ed.). Cengage.

Reports and materials that use this theory (Korean)

There are no materials dedicated to this theory yet, but you can search related reports in the CampusDown library (Korean).

Find more reports · Search '실험설계' on CampusDown →
Threats to Internal ValidityThreats to internal validity explained: Campbell and Stanley's history, maturation, testing, instrumentation, regression, selection, attrition and interactions, with examples and design controls such as random assignment.📚 EducationQuantitative Research MethodsQuantitative research methods explained: measuring phenomena numerically and testing hypotheses with statistics, the research process, experimental, survey and correlational designs, reliability and validity, and limits.👥 SociologyChicago School Urban EcologyChicago School urban ecology explained: Park, Burgess and McKenzie's human ecology, the concentric zone model and zone in transition, invasion and succession, Wirth's urbanism, Shaw and McKay's social disorganization, later models and criticism.👥 SociologyComplexity TheoryComplexity theory explained: systems of many interacting parts from which hard-to-predict order emerges. Emergence, self-organization, nonlinearity and path dependence, the Santa Fe Institute, Schelling's segregation model, applications in sociology and public administration, and limits.👥 Sociology

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This article was last updated on October 15, 2026. It is based on widely recognized original works and textbooks; when citing it in a paper, please check the original sources listed in the references.