# 8.2.2 - Confidence Intervals

Confidence intervals are used to estimate unknown population parameters. Because the population standard deviation ($$\sigma$$) will almost always be unknown in situations in which we are constructing confidence intervals for means, the $$t$$ distribution is used to estimate the sampling distribution. The following pages will show you how to construct a confidence interval for a population mean using formulas and using Minitab Express. Similar to how we computed necessary minimum sample sizes for confidence intervals for proportions, we will also compute the necessary minimum sample size for constructing a confidence interval for a mean.