Use this calculator to compute the confidence interval or margin of error, assuming the sample mean most likely follows a normal distribution. Use the Standard Deviation Calculator if you have raw data only.
A confidence interval is a statistical measure used to indicate the range of estimates within which an unknown statistical parameter is likely to fall. If the parameter is the population mean, the confidence interval is an estimate of possible values of the population mean.
A confidence interval is determined through use of observed (sample) data and is calculated at a selected confidence level (chosen prior to the computation of the confidence interval). This confidence level, such as a 95% confidence level, indicates the reliability of the estimation procedure; it is not the degree of certainty that the computed confidence interval contains the true value of the parameter being studied. Specifically, the confidence level indicates the proportion of confidence intervals, that when constructed given the chosen confidence level over an infinite number of independent trials, will contain the true value of the parameter.