Checking Out Formulas for Confidence Intervals

By Deborah J. Rumsey, David Unger

Part of U Can: Statistics For Dummies Cheat Sheet

In statistics, a confidence interval gives a range of plausible values for some unknown population characteristic. It contains an initial estimate plus or minus a margin of error (the amount by which you expect your results to vary if other samples were taken). The following table shows formulas for the components of the most common confidence intervals and keys for when to use them.