undercoverage

Examples of undercoverage in the following topics:

• Sampling Bias

  • A commonly-cited example of undercoverage is the poll taken by the Literary Digest in 1936 that indicated that Landon would win an election against Roosevelt by a large margin when, in fact, it was Roosevelt who won by a large margin.
  • A detailed analysis by Squire (1988) showed that it was not just an undercoverage bias that resulted in the faulty prediction of the election results.
  • He concluded that, in addition to the undercoverage described above, there was a nonresponse bias (a form of self-selection bias) such that those favoring Landon were more likely to return their survey than were those favoring Roosevelt.

• Telephone Surveys

  • Undercoverage.
  • Undercoverage is a highly prevalent source of bias.

• How Well Do Probability Methods Work?

  • This type of list is often not available, causing most samples to suffer from undercoverage.

• A Closer Look at the Gallup Poll

  • This method prevented problems such as undercoverage, which could occur if Gallup had chosen to select numbers from a phone book (since not all numbers are listed).