Confidence Interval for Proportion Calculator

Uncover the range for your population proportion with ease.

Calculator Inputs

Enter the sample proportion (between 0 and 1).

Enter the sample size (positive integer).

Choose the desired confidence level.

Understanding Confidence Intervals for Proportion

A confidence interval for a proportion is a range of values that is likely to contain the true population proportion. It is used when you want to estimate the proportion of a population that has a certain characteristic, based on a sample from that population.

For example, if you want to know the proportion of people who prefer a certain brand of coffee, you might take a sample of people, ask them their preference, and then calculate a confidence interval for the proportion of people in the entire population who prefer that brand.

The confidence level (e.g., 95%) indicates the probability that the confidence interval contains the true population proportion. A 95% confidence level means that if you were to take many samples and calculate a confidence interval for each sample, about 95% of these intervals would contain the true population proportion.

The formula for a confidence interval for a proportion is typically given by:

$$ CI = p \pm Z \sqrt{\frac{p(1-p)}{n}} $$

This calculator simplifies this process, allowing you to quickly estimate the confidence interval for your proportion data.

Learn more about confidence intervals on resources like Khan Academy or StatTrek.