Short Answer

Suppose a school board claims that because the researcher selected two 'similar' schools for the anti-bullying study, selection effects have been completely controlled for. In 1 to 3 sentences, apply the concept of selection effects to explain why simply selecting 'similar' schools is insufficient to guarantee group equivalence.

Question: Suppose a school board claims that because the researcher selected two 'similar' schools for the anti-bullying study, selection effects have been completely controlled for. In 1 to 3 sentences, apply the concept of selection effects to explain why simply selecting 'similar' schools is insufficient to guarantee group equivalence.

Sample answer: Although the schools may be similar on broad characteristics, the lack of random assignment means individual students still differ systematically between the schools on variables like home environment or personal behaviors. These preexisting individual differences can still create a selection effect that acts as an alternative explanation for any observed differences in bullying.

Key points:

  • Applies the concept of selection effects to show that school-level similarity does not equal individual-level equivalence.
  • Explains that the lack of random assignment allows systematic individual differences to persist between the schools.
  • States that these baseline differences can still explain the differences in bullying.

Feedback: Selecting similar schools does not ensure that the individual students within them are equivalent, because students were not randomly assigned. Preexisting differences at the student level can still cause selection effects that threaten internal validity.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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