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.
Calculators (8)
t-Test Calculator: One-Sample, Two-Sample, Welch, Paired (Free Online)
Free online t-test calculator. Run one-sample, paired, Welch's, and pooled two-sample t-tests on raw data or summary stats. Get t, df, p-value, 95% CI, and Cohen's d.
OpenA/B Test Calculator
Free A/B test calculator. Sample size planning, two-proportion z-test, Bayesian beta-binomial (BF10), sequential sanity check, and lift CI. No signup required.
OpenChi-Square Test Calculator (Independence, Goodness-of-Fit, Homogeneity)
Free chi-square test calculator: independence, goodness-of-fit, and homogeneity. Standardized residuals, Cramer’s V, mosaic plot, and Fisher’s exact handoff.
OpenConfidence Interval Calculator
Free confidence interval calculator: mean, proportion, difference, regression coefficient, Poisson rate, variance, correlation. Wilson, Clopper-Pearson, Newcombe, Welch, exact methods.
OpenBootstrap CI Calculator
Bootstrap confidence interval calculator: percentile, basic, and BCa for mean, median, SD, IQR, quantile, or any custom statistic. 10K+ resamples in your browser.
OpenP-Value Adjustment Calculator: Bonferroni, Holm, BH FDR, Benjamini-Yekutieli
Adjust p-values for multiple comparisons: Bonferroni, Holm, Benjamini-Hochberg FDR, Benjamini-Yekutieli. Paste your p-values and see what stays significant. Free online.
OpenEquivalence / Non-Inferiority Calculator
Plan and analyze equivalence and non-inferiority trials. Two one-sided tests (TOST), 90% CI vs equivalence bounds, and sample size calculation. Free online.
OpenZ-Score Calculator: Z to Percentile, Percentile to Z, Tail Probabilities
Free z-score calculator. Convert raw scores to z, z to percentile, percentile to z, area between two z-values, and one or two-tailed tail probabilities.
OpenBayesian (2)
Bayes Factor Calculator
Bayes factor calculator (BF10, BF01) for t-tests, proportions, and correlations. JZS Cauchy prior with sensitivity plot, posterior P(H1). Free online, no signup.
OpenBayes Theorem Calculator
Update P(H|D) from prior, sensitivity, and specificity. Step-by-step derivation, PPV/NPV, false-positive paradox, spam classifier, and two-test chaining. Free online.
OpenR Output Interpreters (6)
lm() Output Interpreter
Paste R summary(lm(...)) output. Plain-English read of every coefficient, R^2 / F / residual interpretation, and diagnostic callouts. Compare 2+ models with AIC / BIC / anova.
Openglm() Output Interpreter
Paste R summary(glm(...)) output. Plain-English read of coefficients with odds-ratio and rate-ratio conversion. Logistic, Poisson, quasi-binomial, quasi-Poisson, Gamma. Compare 2+ models with deviance / AIC / LRT.
OpenANOVA Output Interpreter
Paste R aov() or car::Anova() output, or any ANOVA table. Plain-English read of every effect, eta-squared and partial eta-squared, Type I vs II vs III explained.
OpenRegression Diagnostic Plot Interpreter: Residuals, Q-Q, Leverage
Interpret regression diagnostic plots: residuals vs fitted, Q-Q, scale-location, and leverage. Verdicts on heteroscedasticity, nonlinearity, normality, outliers, and influence.
OpenVIF / Multicollinearity Calculator (Correlation Matrix or car::vif())
Free VIF and multicollinearity calculator. Paste car::vif() output or a correlation matrix. Traffic-light VIF flags, tolerance, condition number, and GVIF for factors.
OpenConfusion 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 class-imbalance flags.
OpenPickers and Decision Tools (3)
Normality Test Calculator: Shapiro-Wilk, Anderson-Darling, Q-Q Plot
Test whether your data follows a normal distribution: Shapiro-Wilk, Anderson-Darling, Lilliefors, Jarque-Bera. Includes Q-Q plot. Free online calculator.
OpenNon-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.
OpenDAG Confounder Picker
Draw a causal DAG; the picker finds the minimum sufficient adjustment set via Pearl's back-door criterion, flags colliders, and exports a clean DAG diagram.
OpenStudy Design and Power (4)
Power Analysis Calculator
Free statistical power analysis calculator: solve for sample size, power, effect size, or alpha across t-tests, ANOVA, proportions, correlation, and chi-square. Cohen's benchmarks.
OpenSurvival 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.
OpenEffect Size Converter
Free effect size converter: Cohen's d, Hedges' g, Pearson's r, odds ratio, eta-squared, Cohen's f, NNT, CLES. Includes 95% confidence intervals.
OpenType 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 across six test types.
OpenSpecialized (4)
ADF and KPSS Stationarity Test Calculator + ARIMA 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 and get a verdict and ACF/PACF plots.
OpenOutlier Detection Calculator
Detect outliers in a numeric sample using Grubbs, Generalized ESD, Hampel (MAD), or Tukey IQR. Free in-browser calculator with method comparison.
OpenROC / AUC Calculator
Free ROC curve and AUC calculator. DeLong 95% CI, optimal threshold (Youden, F1, cost-weighted), live confusion matrix, and calibration plot.
OpenReprex 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.
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