Proportion Confidence Interval Calculator With Steps

Proportion confidence intervals are crucial in statistics to estimate the population proportion based on a sample. Our calculator simplifies this process with step-by-step guidance.

1. Enter your sample size, proportion, and desired confidence level.
2. Click ‘Calculate’.
3. View the confidence interval and chart below.

The formula used is: Proportion ± (Z * √[(Proportion * (1 - Proportion)) / Sample Size]), where Z is the Z-score corresponding to the chosen confidence level.

Comparison of Confidence Intervals at Different Confidence Levels

Sample Size	Proportion	90% CI	95% CI	99% CI

• Use a larger sample size for more precise estimates.
• Consider the margin of error: a higher confidence level results in a wider interval.

What is a confidence interval?

A confidence interval is a range of values around a sample statistic (like a mean or proportion) that is likely to contain the population parameter.

Learn more about confidence intervals from these authoritative sources: Statistics How To, Penn State University.