Statistics Tools
t-tests, ANOVA, chi-square, correlation, regression, power analysis and effect sizes — free online calculators with plain-language interpretation, automatic assumption checks and APA 7 reporting.
Independent Samples t-Test Calculator
Compare two group means with Welch or Student t-test, effect size, confidence interval and automatic assumption checks.
Paired Samples t-Test Calculator
Test before/after or matched-pair differences with effect size, confidence interval and normality check.
One-Way ANOVA Calculator (+ Tukey HSD)
Compare three or more group means with the full ANOVA table, effect sizes and Tukey HSD post-hoc comparisons.
Two-Way ANOVA Calculator
Test two factors and their interaction with the complete ANOVA table and partial eta squared effect sizes.
Chi-Square Test Calculator
Test of independence for contingency tables and goodness-of-fit test, with Cramér's V and expected counts.
Correlation Calculator (Pearson & Spearman)
Pearson r and Spearman rho together, with significance test, confidence interval and normality check.
Simple Linear Regression Calculator
Fit y = a + bx with coefficient table, R², F-test, confidence intervals and residual normality check.
Power Analysis Calculator: t-Test
A priori sample size and post-hoc power for t-tests — G*Power parameters (d, α, power) in the browser.
Power Analysis Calculator: One-Way ANOVA
Sample size and power for one-way ANOVA from Cohen's f — a browser-based G*Power alternative.
Power Analysis Calculator: Two Proportions
Sample size and power for comparing two proportions (A/B tests, clinical rates) via Cohen's h.
Effect Size Converter (d, r, f, η², OR)
Convert between Cohen's d, r, Cohen's f, eta squared and odds ratio; includes Hedges' g and CLES.
Descriptive Statistics Calculator
Mean, SD, median, quartiles, skewness, kurtosis, SEM and 95% CI — with Shapiro-Wilk normality test.
P-value Calculator
Convert a z, t, chi-square or F test statistic into its exact p-value — one- or two-tailed, with a plain-language verdict.
Confidence Interval Calculator
90/95/99% confidence interval for a mean (t or z) or a proportion — from summary statistics, with margin of error and critical value.
Z-Score Calculator
Standardize a value (x, mean, SD) or enter z directly — percentile rank and left-, right- and two-tailed probabilities included.
Standard Deviation Calculator
Sample (n−1) and population (n) standard deviation and variance in one shot — with SEM, coefficient of variation and sum of squares.
Mann-Whitney U Test Calculator
Non-parametric comparison of two independent groups — U, z and p with tie correction, plus the rank-based effect size r.
Wilcoxon Signed-Rank Test Calculator
Non-parametric paired comparison (before/after) — V, z and p with tie correction; zero differences handled the standard way.
Kruskal-Wallis H Test Calculator
Non-parametric comparison of 3+ independent groups — tie-corrected H, df, p and the effect size ε², with group medians.
Cronbach's Alpha Calculator
Scale reliability from an item-response matrix: raw and standardized α, mean inter-item correlation and alpha-if-item-deleted.
Binomial Probability Calculator
P(X = k) plus all cumulative probabilities (≤, ≥, <, >) for n trials with success probability p — with mean and SD.
Permutation & Combination Calculator
C(n, k) and P(n, k) side by side, with factorials — exact integers up to 15 digits, scientific notation beyond.