About Z-t-Chi Calculator
Interactive visualizations for better understanding
Precise calculations with detailed interpretations
Educational insights and statistical explanations
User-friendly interface for students and professionals
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Run a specific test or compare tests on one dataset.
Z Calculator
Probabilities and areas under the standard normal curve, with shaded-region visualizations.
Open Z Calculatort Calculator
Critical values and p-values for one-sample, paired, and Welch's two-sample t tests.
Open t CalculatorChi-Square Calculator
χ² test of independence for r × c contingency tables, with Cramer's V.
Open Chi-Square CalculatorCompare Tests
Run χ², Fisher's exact, and Z for proportions on the same 2×2 table and see where they diverge.
Open Compare TestsCorrections
Bonferroni, Holm, and Benjamini-Hochberg for a bundle of p-values — plus an interactive chart of Type I inflation.
Open CorrectionsEpidemiology 2×2
Sensitivity, specificity, PPV, NPV, LR+/LR−, RR, OR, NNT — all with CIs from a single 2×2 table.
Open Epi CalculatorStudy
Build intuition with simulation, assumption checks, and real datasets.
Simulation
Bootstrap CIs and permutation p-values on your raw data — see the same conclusion from a second angle.
Open SimulationAssumption Coach
Q-Q plot + skewness + kurtosis + Jarque-Bera + outliers + a traffic-light recommendation on whether parametric tests are appropriate.
Check Your DataCurated Datasets
Classic biostatistics data (Salk vaccine, Physicians' Health Study, Lady Tasting Tea, ...) — one click into any relevant calculator.
Open Dataset LibraryReference
Look up a decision, a symbol, or a common mistake.
User Guide
New here? Start with the decision tree ("which calculator should I use?") and the quick-start walkthroughs.
Open the GuideNotation Translator
Cross-reference textbook notation (μ, x̄, χ²) against SPSS labels, R output, and APA reporting style.
Open the TranslatorError Traps
Fifteen classic mistakes in applied statistics — scenario, why-it-looks-right, what's-actually-wrong, and the fix. Filter by test type.
Open the Library