Confidence Interval Calculator
Enter sample mean, standard deviation, sample size, and confidence level.
Confidence Interval — Formula
Formula
CI = x̄ ± z* × (σ / √n)
Where z* is the critical value (1.645 for 90%, 1.960 for 95%, 2.576 for 99%).
Interpretation
A 95% CI means: if you repeated the study 100 times, 95 of the intervals would contain the true population mean.
