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Literary Digest Poll

Literary Digest Poll. 1936 election: Franklin Delano Roosevelt vs. Alf Landon Literary Digest had called the election since 1916 Sample size: 2.4 million! Prediction: Roosevelt 43% Actual: Roosevelt: 62% (Literary Digest went bankrupt soon after). What went wrong?. Context

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Literary Digest Poll

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  1. Literary Digest Poll • 1936 election: Franklin Delano Roosevelt vs. Alf Landon • Literary Digest had called the election since 1916 • Sample size: 2.4 million! • Prediction: Roosevelt 43% • Actual: Roosevelt: 62% • (Literary Digest went bankrupt soon after)

  2. What went wrong? • Context • 9 million unemployed; real income down 1/3 • Landon: “Cut spending” versus Roosevelt: “Balance peoples’ budgets before government’s budget • Polling • Survey sent out to 10 million people from subscription list, telephone directories, club membership lists • 2.4 million responded

  3. Sources of bias • Sampling frame not representative • Biased toward better off groups (and more Republican) • Voluntary response bias • The anti-Roosevelt forces were angry---and had a higher response rate!

  4. George Gallup did it right • Roosevelt’s percentage • Actual election result: 62% • Literary Digest prediction: 43% • Gallup’s prediction of the Digest prediction (based on sample of 2,000) 44% • Gallup’s prediction of the election result (based on sample of 50,000) 56% • Gallup used Random sampling

  5. The Year the Polls Elected Dewey • 1948: Harry Truman (Dem) vs. Thomas Dewey (Rep) • All major polls predicted Dewey would win by 5 percentage points (even Gallup)

  6. What went wrong? • Quota Sampling • Each interviewer assigned a fixed quota of subjects in certain categories (race, sex, age) • In each category, interviewers free to choose • Left room for human choice---and inevitable bias • Republicans were easier to reach • Had telephones, permanent addresses, “nicer” neighborhoods • Quota sampling abandoned for Random Sampling

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