Calculate statistical confidence intervals for sample means and proportions. Choose confidence level, input sample data, and get results with visualizations.
A confidence interval (CI) is a range of values that is likely to contain a population parameter with a certain level of confidence. It provides more information than a single point estimate by showing the uncertainty around the estimate.
Use the z-distribution when the population standard deviation is known and the sample size is large (n ≥ 30). Use the t-distribution when the population standard deviation is unknown and must be estimated from the sample data.