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Confidence Interval

  1. Joseph S. Rossi

Published Online: 30 JAN 2010

DOI: 10.1002/9780470479216.corpsy0218

Corsini Encyclopedia of Psychology

Corsini Encyclopedia of Psychology

How to Cite

Rossi, J. S. 2010. Confidence Interval. Corsini Encyclopedia of Psychology. 1–2.

Author Information

  1. University of Rhode Island

Publication History

  1. Published Online: 30 JAN 2010


The concept of the confidence interval was introduced and developed theoretically by Jerzy Neyman in the 1930s. The confidence interval indicates the degree of certainty that a specified range of values around a parameter estimate contains the true value of the population parameter. The upper and lower boundaries of the range are the confidence limits. The width of the confidence interval indicates the degree of precision associated with the parameter estimate. Wider intervals indicate less precision, and narrower intervals indicate greater precision. The width of the interval can never be zero, because there will always be some sampling error associated with estimating a population parameter from sample data. Sampling error may be due to measurement unreliability or other chance factors that cause fluctuations from sample to sample. The result is that, no matter how carefully a sample is drawn or how large it is, one can never be certain that the sample estimate is exactly equal to the parameter (population) value.


  • probability;
  • significance testing;
  • statistics in psychology