# Confidence Prediction

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- September 16, 2005 at 5:36 am #40711
What’s the difference between confidence and prediction intervals? Why does fitted regression plot show wider prediction intervals than confidence intervals?

0September 16, 2005 at 6:08 am #126961

Mike WalmsleyParticipant@Mike-Walmsley**Include @Mike-Walmsley in your post and this person will**

be notified via email.I hope this helps. It is an excerpt from Statsofts electronic textbook.

Confidence Interval vs. Prediction Interval. In regression, it is possible to predict the value of the dependent variable based on given values of the independent variables. When these values are predicted, it is also possible to calculate confidence intervals and/or prediction intervals for the dependent variable.

The confidence interval gives information on the expected value (mean) of the dependent variable. That is, a confidence interval for a predicted value of the dependent variable gives a range of values around which the “true” (population) mean (of the dependent variable for given levels of the independent variables) can be expected to be located (with a given level of certainty, see also Elementary Concepts).

The prediction interval gives information on individual predictions of the dependent variable. That is, a prediction interval for a predicted value of the dependent variable gives us a range of values around which an additional observation of the dependent variable can be expected to be located (with a given level of certainty, see also Elementary Concepts).

Note that the confidence interval will produce a smaller range of values, because it is an interval estimate for an average rather than an interval estimate for a single observation. See Neter, Wasserman, & Kutner, 1985.0September 16, 2005 at 6:33 am #126966Thanks very much for the clear explanation.

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