Confidence Interval Calculator

For means, proportions, and differences between groups.

Select Analysis Type One-Sample Mean One-Sample Proportion Two-Sample Mean Difference (Independent) Two-Sample Proportion Difference Paired Sample Mean Difference

Sample Data

Sample Mean (x̄)

Sample Std. Dev. (s)

Sample Size (n)

Options

Distribution

t-distribution (recommended) z-distribution (n > 30)

Sample Data

Sample Proportion (p̂) or # of Successes (x)

Sample Size (n)

Options

Method

Normal Approximation Exact (Clopper-Pearson) (planned)

Group 1 Data

Mean (x̄₁)

Std. Dev. (s₁)

Size (n₁)

Group 2 Data

Mean (x̄₂)

Std. Dev. (s₂)

Size (n₂)

Options

Variance Assumption

Unequal variances (Welch's) Equal variances (Pooled)

Group 1 Data

Proportion (p̂₁) or # of Successes (x₁)

Size (n₁)

Group 2 Data

Proportion (p̂₂) or # of Successes (x₂)

Size (n₂)

Paired Differences Data

Mean of Differences (d̄)

Std. Dev. of Differences (s_d)

Number of Pairs (n)

Confidence & Precision

Confidence Level (%)

Decimal Precision 0 1 2 3 4

Population Size (N) (optional FPC)

Privacy Note: All calculations are performed on your device. No data is sent to our servers.

Disclaimer: This calculator is for educational and planning purposes only. It is not a substitute for professional statistical advice.