Methods

Randomized experiment

A researcher deliberately changes a condition and uses a chance process to allocate participants to conditions. The comparison asks whether the intervention changes an outcome while reducing systematic baseline differences between groups. Randomization strengthens causal inference; the quality of measurement, implementation, follow-up and the comparison condition still matters.

Does a brief retrieval exercise improve later recall compared with rereading the same material?

How it works

  1. For a synthetic classroom project, define recall as the number of ideas reproduced on a delayed test. Prepare the same passage for both groups and specify when they study, how long they work and when the test occurs. Decide the comparison before viewing results.
  2. Recruit participants, then allocate them using a genuinely random sequence to retrieval practice or rereading. Keep recruitment separate from allocation: selecting volunteers answers who entered the study; random assignment answers which condition each volunteer received. Record departures from the planned procedure.
  3. Use the same delayed test and scoring rules for both groups. Compare outcomes with uncertainty and report missing tests. Check whether different instructions, extra feedback or unequal study time could have created a second difference besides the intended learning activity.

Evidence: (Research Methods in Psychology: Experiment Basics, n.d.); (Research Methods in Psychology: Experimental Design, n.d.)

Retrieval practice versus rereading

Teaching scenario

This teaching scenario proposes random allocation to two study activities and a later memory test. No data were collected and no improvement is being claimed. If the retrieval group performed better, the first interpretation would concern these specific activities, this passage and this recruited group. A broader claim about all students or all learning would require additional evidence.

This example is constructed for learning. It does not report an observed research result.

What can you conclude?

A well-executed randomized comparison can support a causal claim about the assigned intervention under the study conditions.

Evidence: (Research Methods in Psychology: Experiment Basics, n.d.); (Research Methods in Psychology: Experimental Design, n.d.)

Limits and common mistakes

  • Random assignment does not make a volunteer sample representative of a whole population.
  • Noncompliance, differential dropout, weak measures or a confounded comparison can undermine the intended interpretation.

A mistake to catch

Treating random assignment as random sampling, or assuming that the word randomized guarantees a trustworthy conclusion.

Evidence: (Research Methods in Psychology: Experiment Basics, n.d.); (Research Methods in Psychology: Experimental Design, n.d.)

Sources and inspection notes

Links checked October 21, 2026. Inspection scope is stated for each source; an access date is not a publication date.

  1. Research methods in psychology: Experiment basics. (n.d.). https://opentextbc.ca/researchmethods/chapter/experiment-basics/

    Randomized experiment: summary, procedure 1 and 3, allows, limits 2; manipulation, confounding and external validity Open teaching chapter by the textbook authors, read 21 October 2026. Not a primary empirical study.

  2. Research methods in psychology: Experimental design. (n.d.). https://opentextbc.ca/researchmethods/chapter/experimental-design/

    Randomized experiment: procedure 2 and pitfall (sampling versus assignment). Within-subjects: summary, procedure, allows, limits, pitfall (carryover and counterbalancing) Open teaching chapter by the textbook authors, read 21 October 2026. Not a primary empirical study.

Keep reading

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020). Psychology 2e. OpenStax. https://openstax.org/books/psychology-2e/pages/2-3-analyzing-findings

Nearest related OpenStax Psychology 2e reading. This is a course connection, not evidence for every specialist detail above.

Specialist reading: Research methods in psychology: Experiment basics. (n.d.). https://opentextbc.ca/researchmethods/chapter/experiment-basics/

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