Confidence Level


  • As part of a Statistical Estimate, the chance that a Confidence Interval derived from a Random Sample will include the true value. For example, “95% Confidence” means that if one were to draw 100 independent Random Samples of the same size, and compute the Confidence Interval from each Sample, about 95 of the 100 Confidence Intervals would contain the true value. It is important to note that the Confidence Level is not the Probability that the true value is contained in any particular Confidence Interval; it is the Probability that the method of estimation will yield a Confidence Interval that contains the true value. 1
  • How often we would achieve a similar result if we repeated the same process many times. If we did the same kind of test from the same population more than once, the confidence level would tell us how often we would get a result that is within a certain range (the confidence interval) of the true value for the population. Most scientific studies employ a minimum confidence level of 0.95, meaning that 95 percent of the time when you repeated the experiment you would find a similar result. The higher the confidence level the larger the sample size that is required. Technically, it is the proportion of times when the true population value would be included within the confidence interval. 2 3


  1. Maura R. Grossman and Gordon V. Cormack, EDRM page & The Grossman-Cormack Glossary of Technology-Assisted Review, with Foreword by John M. Facciola, U.S. Magistrate Judge2013 Fed. Cts. L. Rev. 7 (January 2013).
  2. Herb Roitblat, Search 2020: The Glossary.
  3. Herb Roitblat, Predictive Coding Glossary.