Statistical Tools

Twenty-seven free, browser-based calculators and interpreters that do exactly one statistical job each. Run a t-test, plan an A/B test, paste a summary(lm) output, correct for multiple testing. Every tool shows the formula, the matching R code, and a plain-language inference banner so you can copy results into a report without second-guessing.

27 tools · 6 categories · 100% free · No signup

Calculators (8)

t-Test Calculator

One-sample, two-sample (Welch + pooled), and paired t-tests. Raw data or summary stats. t / df / p / 95% CI / Cohen's d / verdict, with reproducible R. Runs in your browser.

A/B Test Calculator

Plan and analyze A/B tests: two-proportion z-test, Bayesian beta-binomial, sequential sanity check. Sample size, lift, CI, p, BF10. Reproducible R code, runs in your browser.

Chi-Square Test Calculator

Run a chi-square test of independence, goodness-of-fit, or homogeneity. Standardized residuals, Cramer's V, mosaic plot, Fisher's exact handoff, and reproducible R code.

Confidence Interval Calculator

Compute a confidence interval for a mean, proportion, difference, regression coefficient, Poisson rate, variance, or correlation. Includes Wilson, Clopper-Pearson, Newcombe, Welch, exact methods. Reproducible R code, runs in your browser.

Bootstrap CI Calculator

Run percentile, basic, and BCa bootstrap confidence intervals for the mean, median, SD, IQR, quantile, or any custom statistic. Paste raw data and the calculator does the resamples in your browser. Reproducible R code via boot::boot().

Multiple Testing Correction Calculator

Adjust p-values for multiple comparisons: Bonferroni, Holm, Benjamini-Hochberg FDR, Benjamini-Yekutieli. Paste your p-values, see what's still significant, copy reproducible R. Runs in your browser.

Equivalence / Non-Inferiority Calculator

Plan and analyze equivalence and non-inferiority trials. Two one-sided tests (TOST), 90% CI vs equivalence bounds, sample size, with reproducible R code that runs in your browser.

Z-Score & Percentile Calculator

Convert raw scores to z-scores, z to percentile, percentile to z, area between two z, and one or two-tailed tail probabilities. Reproducible R code, runs in your browser.

Bayesian (2)

Bayes Factor Calculator

Compute JZS Bayes factors (BF10 / BF01) for two-sample t, one-sample t, proportion, and correlation tests. Cauchy prior with sensitivity plot, posterior P(H1), and reproducible R via the BayesFactor package.

Bayes Theorem Calculator

Update P(H|D) from prior, sensitivity, specificity. Step-by-step derivation, PPV/NPV, false-positive paradox, spam classifier, two-test chaining. Reproducible R, runs in your browser.

R Output Interpreters (6)

lm() Output Interpreter

Paste R summary(lm(...)) output. Plain-English read of every coefficient, R^2 / F / residual interpretation, diagnostic callouts. Compare 2+ models with AIC / BIC / anova. Reproducible R code.

glm() Output Interpreter

Paste R summary(glm(...)). Plain-English read of coefficients with odds-ratio / rate-ratio conversion. Logistic, Poisson, quasi-binomial, quasi-Poisson, Gamma. Compare 2+ models with deviance / AIC / LRT. Reproducible R.

ANOVA Output Interpreter

Paste R aov() or car::Anova() output. Plain-English read of every effect, eta-squared and partial eta-squared, Type I vs II vs III explanation, and reproducible R code.

Diagnostic Plot Interpreter

Paste residuals + fitted values from your R lm() / glm() fit. Get verdicts on heteroscedasticity, nonlinearity, normality, outliers, and influence; mini plot.lm() previews; reproducible R code.

VIF / Multicollinearity Interpreter

Paste car::vif() output or a correlation matrix; get traffic-light VIF flags, tolerance, condition number, GVIF support for factors, plain-English read of every problem predictor. Reproducible R code, runs in your browser.

Confusion Matrix Interpreter

Paste a confusion matrix; get accuracy, precision, recall, F1, MCC, kappa, balanced accuracy. Plain English read of which metric to trust when, with reproducible R.

Pickers and Decision Tools (3)

Normality Test Picker

Test whether your data follows a normal distribution: Shapiro-Wilk, Anderson-Darling, Lilliefors, Jarque-Bera. Q-Q plot. Reproducible R code. Runs in your browser.

Non-Parametric Test Picker

Pick the right rank-based test (Mann-Whitney U, Wilcoxon signed-rank, Kruskal-Wallis, Sign test) and run it on raw data. Test statistic, p-value, effect size, and Hodges-Lehmann CI in your browser, with reproducible R.

DAG Confounder Picker

Draw a causal DAG; the picker identifies the minimum sufficient adjustment set via Pearl's back-door criterion, flags colliders, and emits dagitty R code.

Study Design and Power (4)

Power Analysis Calculator

Solve for sample size, power, effect size, or alpha across t-tests, ANOVA, proportions, correlation, and chi-square. Cohen's benchmarks. Reproducible R code. Runs in your browser.

Survival Analysis Power Calculator

Plan a time-to-event clinical trial. Compute required events, sample size, or power for a log-rank test using Schoenfeld, Lakatos, or Freedman formulas with accrual, follow-up, and dropout.

Effect Size Converter

Convert between effect sizes: Cohen's d, Hedges' g, Pearson's r, odds ratio, η², Cohen's f, NNT, CLES. With CIs and reproducible R code. Runs in your browser.

Type I / II Error Visualizer

Visualize Type I and Type II errors with live overlapping sampling distributions. Drag effect, n, alpha; watch beta shrink and power rise. Six test types. Reproducible R code, runs in your browser.

Specialized (4)

Time Series Stationarity & Order Picker

Run ADF and KPSS stationarity tests, suggest differencing order, and rank ARIMA(p,d,q) candidates by AICc. Paste a 1-D series, get a verdict, ACF/PACF plots, and reproducible R code.

Outlier Detection Calculator

Detect outliers in a numeric sample using Grubbs, Generalized ESD, Hampel (MAD), or Tukey IQR. Reproducible R code, runs in your browser.

ROC / AUC Calculator

Paste outcomes + predicted scores; get ROC curve, AUC with DeLong 95% CI, optimal thresholds (Youden / F1 / cost-weighted), live confusion matrix, calibration. Reproducible R code.

Reprex Builder

Paste raw R code; get a clean, minimal, self-contained reproducible example. Lints for missing libraries, custom data without dput(), file reads, and seed gaps. Markdown-ready output.

Looking for the matching R tutorials? Browse the full compendium of long-form articles on probability, regression, ANOVA, time series, and machine learning in R.