T-tests, confidence intervals, regression, correlation, chi-square, ANOVA — all free, instant, and accurate. No spreadsheet needed.
Interactive games & simulators that make statistics actually click — not just calculators.
Error bars for eval scores, paired tests to compare models, eval sample size, pass@k, and LLM-judge agreement.
Mean, median, mode, standard deviation, variance, IQR, skewness, kurtosis, and more.
Calculate PDF, CDF, z-scores, and tail probabilities for any normal distribution.
One-sample, two-sample (independent), and paired t-tests with p-values and interpretation.
Goodness of fit and independence tests. Includes Cramér's V effect size.
Compare means across three or more groups. F-statistic and p-value included.
CI for a population mean (t-distribution) or proportion. Choose your confidence level.
Required sample size for estimating a mean or proportion with a given margin of error.
Pearson and Spearman correlation coefficients with confidence intervals and scatter chart.
Simple linear regression with R², slope, intercept, residuals, and regression chart.
Convert any value to a z-score, find its percentile rank, and calculate tail probabilities.
Non-parametric alternative to the t-test. No normality assumption needed.
Quantify practical significance with Cohen's d and Hedge's g. Visual overlap chart included.
P(X=k), P(X≤k), P(X≥k) for any binomial distribution with full distribution table and chart.
Compare two sample proportions — ideal for A/B tests and clinical trial response rates.
Probability of k events given an average rate λ, with full table and PMF chart.
Two events — AND, OR, conditional, and "at least one" — with a live Venn diagram.
Compute nPr, nCr, and factorials exactly, with a binomial-coefficient chart.
OR, RR, absolute risk reduction, and NNT from a 2×2 table, with 95% confidence intervals.
New to a topic? Read the plain-English guides → · Revising? Grab the printable statistics formulas cheat sheet → · Not sure which test? Use the chooser →
Built for students, researchers, analysts, and everyone in between.
Powered by a Python/SciPy backend for numerically accurate outputs — no rounding errors.
Every result includes a plain-English conclusion so you know what the numbers actually mean.
Create a free account to save your calculation history, revisit results, and stay organized.
Fully responsive — works great on desktop, tablet, and mobile browsers.