Case Study

Analyze this case study by drawing direct parallels to the 1936 presidential election poll between the Literary Digest and George Gallup. Diagnose the primary methodological flaw in the subscription-list survey, explain how the university team's approach mirrors Gallup's scientific methods, and determine which poll is scientifically more credible.

Case context: A modern polling group wants to predict the outcome of a state senate election. They send out 2 million digital survey ballots to individuals on an expensive investment newsletter subscription list. Meanwhile, a university research team conducts a survey of 1,500 randomly selected registered voters across all income brackets. The subscription-list survey predicts Candidate A will win in a landslide, while the university team predicts Candidate B will win.

Question: Analyze this case study by drawing direct parallels to the 1936 presidential election poll between the Literary Digest and George Gallup. Diagnose the primary methodological flaw in the subscription-list survey, explain how the university team's approach mirrors Gallup's scientific methods, and determine which poll is scientifically more credible.

Sample answer: The subscription-list survey suffers from severe selection bias, directly paralleling the Literary Digest's 1936 straw poll, because its sample is drawn from an investment newsletter, which overrepresents wealthier individuals. The university team's approach mirrors George Gallup's scientific methods because it uses a much smaller, representative sample that spans all income levels, including less wealthy individuals. Therefore, the university team's poll is scientifically more credible because representative sampling is far more important for accuracy than raw sample size.

Key points:

  • Diagnose the selection bias in the subscription-list survey (overrepresenting wealthier individuals).
  • Compare the subscription-list survey to the Literary Digest's biased 1936 straw poll.
  • Contrast the massive, biased sample with the smaller, representative sample of the university team.
  • Determine that the university team's poll is more credible due to scientific survey methodology.

Rubric: The analysis must diagnose selection bias in the subscription survey, link it to the Literary Digest's methods, explain how the university team's inclusion of all income brackets mirrors Gallup's scientific sampling, and conclude that the smaller, representative poll is more credible.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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