confidence interval A range of values about a parameter estimate such that the probability that the true value of the parameter lies within the range is some fixed value, α, known as the confidence level. The upper and lower limits of the range are known as confidence limits. Confidence limits are calculated from the theoretical frequency distribution of the estimating function. The concept may be generalized to several parameters. A confidence region at level α contains the true values of the parameters with probability α.

confidence interval In statistics, a range of values based on the observed data which are likely to contain the true unknown value for a specified proportion of the time (confidence level) usually expressed as a percentage.