Case Study

Diagnose the methodological flaw in the Literary Digest's sampling frame. Explain how the choice of databases for the mailing lists introduced sampling bias and why this led to an incorrect prediction of the election's outcome.

Case context: In 1936, the Literary Digest attempted to forecast the U.S. presidential election between Alf Landon and Franklin Roosevelt by mailing straw poll ballots to millions of Americans. Their mailing lists were compiled largely from telephone directories and registries of automobile owners. Based on this methodology, the editors predicted a landslide victory for Alf Landon. However, Landon lost by a wide margin, and the poll is now famous as a major failure in survey methodology.

Question: Diagnose the methodological flaw in the Literary Digest's sampling frame. Explain how the choice of databases for the mailing lists introduced sampling bias and why this led to an incorrect prediction of the election's outcome.

Sample answer: The Literary Digest's sampling frame suffered from severe sampling bias because it relied on telephone directories and registered automobile owners. During 1936, telephones and automobiles were luxury items owned predominantly by wealthier individuals. Consequently, the sample over-represented wealthier people, who were more likely to vote for Alf Landon. Because the sample did not accurately represent the broader, less-wealthy voting public who favored Franklin Roosevelt, the poll's results were biased, leading to an incorrect landslide prediction.

Key points:

  • Identified the sampling frame error (using telephone and car registration lists).
  • Explained that the sampling frame over-represented wealthier individuals.
  • Connected the socioeconomic status of the respondents to their preference for Alf Landon.
  • Explained that the resulting sampling bias invalidated the prediction.

Rubric: Grading criteria: 1. Identifies the sampling frame flaw (reliance on telephone directories and automobile registries). 2. Explains that this over-represented wealthier individuals. 3. Links wealth to a preference for Landon. 4. Explains how this bias resulted in a skewed sample that failed to reflect the actual electorate.

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Updated 2026-05-26

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Research Methods in Psychology - 4th American Edition @ KPU

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