Confidence Interval Calculator
Calculate the confidence interval for a population mean using a sample's mean, standard deviation, and size.
About Confidence Intervals
A confidence interval gives a range that, with a stated probability (e.g., 95%), contains the true population parameter. CI = x̄ ± z(σ/√n). Common z-values: 90% = 1.645, 95% = 1.96, 99% = 2.576.
Inputs
Sample Mean (x̄)
Standard Deviation (σ)
Sample Size (n)
Confidence Level
Result
Lower Bound
71.42
Upper Bound
78.58
Margin of Error
3.58
Z value
1.960
Standard Error
1.826
95% CI: 75 ± 3.58 → (71.42, 78.58)