A **confidence interval** is an interval defined by two values, called confidence limits, calculated from sample data using a procedure which ensures that the unknown true value of the quantity of interest falls between such calculated values in a specified percentage of samples.

Commonly, the specified percentage is 95%; the resulting **confidence interval** is then called a 95% **confidence interval**. A one-sided **confidence interval** is defined by a single calculated value called an upper (or lower) confidence limit. "The numerical interval constructed around a point estimate of a population parameter, combined with a probability statement (the confidence coefficient) linking it to the population's true parameter value. If the same **confidence interval** construction technique and assumptions are used to calculate future intervals, they will include the unknown population parameter with the same specified probability" (QAMS 1993, 6). (See related: confidence coefficient.)

**List of books: Confidence,interval**