# Confidence Interval Calculator

What is the range of confidence?
A confidence interval is a range of values that can contain the true value of the parameter being researched in statistics. It is created using observed data and estimated at a desired level of confidence. The confidence level, such as a 95% confidence level, refers to the accuracy of the estimating process rather than the degree of assurance that the computed confidence interval accurately represents the true value of the parameter under investigation. Prior to computing the confidence interval, the desired confidence level is selected. It displays the percentage of confidence intervals that, when formed given the selected confidence level over an infinite number of independent trials, will include the parameter's actual value.

Confidence interval calculation:

In order to calculate a confidence interval
The sample mean (X) and, if applicable, the population standard deviation () must be known. When the sample size is more than 30, the sample standard deviation, s, can be used in place of the population standard deviation. The population standard deviation and the sample standard deviation will be similar for samples with a size greater than 30. There are various equations that can be used to determine the confidence interval, depending on which standard deviation is known. For the purposes of this calculator, it is assumed that the population standard deviation is known or that the sample size is sufficiently large so that the standard deviations for the population and the sample are comparable.