hard · MCAT psych-soc
A researcher wants to test whether a new tutoring app improves standardized test scores. She recruits students who scored unusually low on a practice test, gives all of them the app for one month, and finds their scores rose substantially on a retest.
Which explanation, other than the app's effectiveness, most plausibly accounts for the score increase, and why is it especially likely in this design?
- Selection bias, because students were not randomly assigned to a control group.
- Regression to the mean, because the sample was deliberately selected for extreme low scores.
- The Hawthorne effect, because students knew they were being observed while using the app.
- Maturation, because students naturally improve in test-taking ability with the passage of one month.
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