🎯 Confidence Interval Calculator
Enter your sample mean, standard deviation, and sample size to calculate a confidence interval at your chosen confidence level.
What This Calculator Does
A confidence interval gives a range around a sample mean that is likely to contain the true population mean, at a chosen confidence level such as 95%.
The Formula
The interval is calculated as mean ± (z × standard error), where standard error = standard deviation / √n, and z is the critical value for your chosen confidence level (1.645 for 90%, 1.96 for 95%, 2.576 for 99%). This calculator uses the standard z-based method, which works well when the sample size is reasonably large (n ≥ 30) or the population standard deviation is known.
Interpreting the Result
A 95% confidence interval means that if you repeated the sampling process many times, about 95% of the resulting intervals would contain the true population mean. A wider interval reflects more uncertainty, usually from a smaller sample or larger variability.
Note: This tool is intended for general educational and planning purposes, not for formal statistical publication.