Confidence Intervals for the Percentage of Even Digits

  • Richard L. Scheaffer
  • Ann Watkins
  • Mrudulla Gnanadesikan
  • Jeffrey A. Witmer
Part of the Textbooks in mathematical sciences book series (TIMS)


Suppose a political poll says that 56% of voters approve of the job the president is doing and that .this poll has a margin of error of 3%. The 3% margin of error results from the fact that the poll was taken from a sample of voters. Since not all voters were included, there is some error due to sampling, or sampling error. If all voters had been asked, the polling organization predicts that the percentage would have been in the confidence interval of 53% to 59%. For every 100 polls that report a 95% confidence interval, the polling organization expects that 95 of the confidence intervals will contain the true population percentage. In this activity you will take a “poll” of random digits in order to estimate the percentage that are even.


Confidence Interval Stochastic Process Systematic Error Sampling Error Statistical Association 
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    David S. Moore (1985), Statistics: Concepts and Controversies, second ed., New York: Freeman.Google Scholar

Copyright information

© Springer Science+Business Media New York 1996

Authors and Affiliations

  • Richard L. Scheaffer
    • 1
  • Ann Watkins
    • 2
  • Mrudulla Gnanadesikan
    • 3
  • Jeffrey A. Witmer
    • 4
  1. 1.University of FloridaUSA
  2. 2.California State UniversityNorthridgeUSA
  3. 3.Fairleigh Dickinson UniversityUSA
  4. 4.Oberlin CollegeUSA

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