Browse 28 free calculators in the Statistics category.
Fisher's Exact Test Calculator - Is 9 of 12 against 4 of 15 a real difference? Type the four counts of a 2x2 table and get the exact p-value, the odds ratio with its interval, the risk ratio and the smallest expected count.
Wilcoxon Test Calculator - Signed-rank for before-and-after data, rank-sum (Mann-Whitney U) for two groups: exact p-values, the typical shift in your own units, and an answer one outlier cannot overturn.
Interquartile Range Calculator - Paste a list and get Q1, the median, Q3 and the IQR, the 1.5 x IQR outlier fences and a box plot, with the same data run through the Excel, TI-84, R and SPSS quartile rules side by side.
Mode Calculator - Which value turns up most often? Paste numbers or words to get the mode with its count and share, see bimodal and no-mode lists named as such, and group measurements that never repeat.
Percentile Calculator - Why do Excel, SPSS and a textbook give different 90th percentiles? Paste your numbers to get a percentile or a percentile rank by all three methods, with the Excel figures and #NUM! cases.
Coefficient of Variation Calculator - Is a standard deviation of 569 big or small? Paste your numbers to get the coefficient of variation with the Excel formula, or compare two data sets and see whether their CVs really differ.
Pearson Correlation Calculator - How closely do two lists move together in a straight line? Get Pearson's r with its p-value and confidence interval, a Spearman check beside it and a warning when one pair drives the result.
Skewness Calculator - Measure how lopsided a list of numbers is: sample and population skewness as Excel and SPSS print them, a D'Agostino p-value, and a check on how much one extreme value drives the result.
Kurtosis Calculator - Tail weight of a list of numbers in four formulas, from Excel KURT to Pearson's b2, with the Anscombe-Glynn test, a normality check and the benchmark distribution the tails resemble.
Linear Regression Calculator - Which straight line fits your data, and how far can you trust it? Get the least-squares equation, a test of the slope, R squared and a forecast with intervals from two lists or pasted columns.
R Squared Calculator - Turn predictions, sums of squares or a reported value into R squared, adjusted R squared and an F test, and see why Excel RSQ and scikit-learn r2_score disagree on the same data.
Z-Score Calculator - Z-scores four ways: one value against a mean and SD, every value in a list with outlier flags, z to percentile and percentile to z, plus T-score, stanine and NCE for test reports.
One-Sample T-Test Calculator - Test a sample mean against a target, a label or a norm. Paste the data or type mean, SD and n to get t, p, the confidence interval, Cohen's d, Hedges' g and the n needed for 80% power.
Two-Sample T-Test Calculator - Compare two means with Welch's, Student's or the paired t-test. Every result shows the test you did not pick next to yours, plus the interval, Cohen's d, Hedges' g and the group size for 80% power.
P-Value Calculator - Already have a test statistic? Type z, t, chi-square or F with its degrees of freedom to get the exact p-value, or switch modes for critical values at 0.05, 0.01 or your own Bonferroni alpha.
Z-Test Calculator - Did variant B really convert better, or is the lift noise? Run a two-proportion, one-proportion or known-sigma mean z-test and get z, p, the interval, Cohen's h and the traffic needed.
Chi-Square Calculator - Paste a table of counts or a list of category totals to test independence or goodness of fit. Returns chi-square, p, Cramér's V, a residual per cell and, for 2x2 tables, the odds ratio and Yates.
Sample Size Calculator - Survey responses for a chosen margin of error, measurements for a mean, or people per group for an A/B test or a t-test, with finite population, response rate and dropout built in.
Confidence Interval Calculator - Find the range a true mean or rate most likely falls in, from raw data, a mean with its SD, or a count. Wilson, exact and Wald intervals side by side, one-sided bounds and a small-population correction.
Standard Error Calculator - The standard error of the mean from raw data, an SD and n, or a count, plus the reverse: SD from a reported SEM or from a 95% confidence interval, and the sample needed for a target precision.
Grouped Data Quartile Calculator - Only have a frequency table with classes and counts? Get Q1, the median, Q3 and any percentile by interpolation, with the cumulative table, every step written out, and gaps or open classes handled.
Conditional Probability Calculator - What is P(A | B) when you only know P(B | A)? Six modes cover two-way tables, the definition, Bayes' theorem, two or three hypotheses and diagnostic tests, all in exact fractions.
ANOVA Calculator - Run a one-way ANOVA on 2 to 10 groups from raw values or from sizes, means and SDs, and get the full ANOVA table, effect size, Welch's test and an equal-variance check.
Kruskal-Wallis Test Calculator - Kruskal-Wallis H test for 2 to 10 independent groups from pasted values, with the tie correction, an exact p-value for small samples and Dunn's pairwise comparisons.
Tukey HSD Calculator - Which group means differ after a significant ANOVA? Run Tukey HSD from raw values, a summary table or means plus MSE and get q, HSD and every pair's interval and p.
Poisson Distribution Calculator - Exactly k, at most k, at least k or between a and b events when all you know is the average rate λ, with the whole Poisson distribution table and the mean, SD and most likely count.
Binomial Distribution Calculator - How likely are 2 sixes in 10 rolls? Get exactly, at most, at least or a range of k successes in n trials, with the exact fraction, the formula filled in and the full distribution table.
Exponential Distribution Calculator - Plan around waiting times, not averages: the chance the next event comes within t, after t or between a and b, and the wait that covers 90% or 95% of cases, from a mean time or a rate.