Confidence Interval Calculator
Calculate confidence intervals for population means and proportions with various confidence levels
About this calculator
A confidence interval calculator helps you determine the range of values within which a population parameter (like mean or proportion) is likely to fall with a specified level of confidence. This statistical tool is essential for researchers, analysts, and students who need to estimate population characteristics based on sample data. By calculating confidence intervals, you can quantify the uncertainty in your estimates and make more informed decisions about your data analysis and hypothesis testing.
How to use
Enter your sample data including sample size, sample mean or proportion, and standard deviation. Select your desired confidence level (commonly 90%, 95%, or 99%). The calculator will automatically compute the margin of error and display the confidence interval range, showing both the lower and upper bounds of your estimate.
Frequently asked questions
What confidence level should I choose?
95% is most common for general research, while 99% provides higher certainty but wider intervals, and 90% gives narrower ranges with less certainty.
What's the difference between mean and proportion intervals?
Mean intervals estimate average values of continuous data, while proportion intervals estimate percentages or rates in categorical data with binary outcomes.
Why do I need a minimum sample size?
Larger samples provide more reliable estimates. Generally, n≥30 for means and n≥10 successes/failures for proportions ensure valid confidence interval calculations.