# Confidence intervals (one sample)

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Confidence intervals give us a range of plausible values for some unknown value based on results from a sample. This topic covers confidence intervals for means and proportions.

A confidence interval for a proportion estimates what percent of a population fits some category based on a results from a sample. For example, if 70 adults own a cell phone in a random sample of 100 adults, we can be fairly confident that the true percentage in the population is somewhere between 61% and 79%. Go through this tutorial to learn how to calculate confidence intervals like this.

A confidence interval for a mean estimates a population mean based on the results from a sample. Go through this tutorial to learn how to calculate confidence intervals using sample mean and sample standard deviation.