## What is a confidence interval?

## Answer

A confidence interval gives you a range of values that you believe the population parameter falls in. Often you will be asked to find a \(100(1-\alpha)%\) confidence interval, where \(1- α\) is a quantity between 0 and 1 that represents the level of confidence. The confidence level is used to determine how often the true parameter falls within the confidence interval. For example, if \(1-\alpha= 0.95\) , you have a 95% confidence interval. This means that, if we calculate intervals for a large number of samples, the true parameter falls in approximately 95% of the intervals.