Confidence Interval Calculator
Estimate a confidence interval for a population mean from a sample mean, sample standard deviation and sample size.
Estimated Confidence Interval0 to 0
Margin of Error0
Standard Error0
Confidence Level95%
How to Use the Confidence Interval Calculator
Enter the sample statistic, variability, sample size and confidence level to estimate an interval around the sample result.
Practical Example
A sample mean of 50 with an appropriate standard error can produce a 95% confidence interval that expresses the estimate plus and minus a margin of error.
Factors That Affect the Result
Sample size, variability, confidence level and the statistical distribution used determine interval width.
Frequently Asked Questions
Does 95% confidence mean a 95% probability for one fixed interval?
Not in the frequentist definition; it describes the long-run performance of the interval procedure.
What makes an interval narrower?
Larger samples and lower variability generally narrow the interval.
Does a higher confidence level widen the interval?
Yes, all else equal.