Statistics calculators
59 free statistics tools, each with the formula and step-by-step working.
- ANOVA Calculator (One-Way)Compare three groups at once with F, p and eta squared.
- Average CalculatorMean, median, mode and range from a list.
- Bayes Theorem CalculatorTurn a test result into a real posterior probability.
- Binomial Distribution CalculatorProbability of k successes in n trials.
- Card Draw Probability CalculatorProbability of drawing specific cards from a standard deck.
- Chi Square CalculatorGoodness of fit test statistic.
- Chi-Square Goodness of Fit CalculatorCompare observed vs expected category counts.
- Chi-Square Test CalculatorGoodness-of-fit test from observed and expected counts.
- Coefficient of Variation CalculatorRelative variability — compare spread across different scales.
- Cohen's D CalculatorStandardised effect size from two group means.
- Conditional Probability CalculatorP(A|B) from P(A and B) and P(B).
- Confidence Interval CalculatorMargin of error and interval around a sample mean.
- Confidence Interval for a Proportion CalculatorConfidence interval around a sample proportion.
- Correlation Coefficient CalculatorPearson r for two data sets.
- Covariance CalculatorHow two variables move together, before standardising.
- Dice Sum Probability CalculatorProbability of rolling a specific sum with two dice.
- Empirical Rule CalculatorTurn a mean and standard deviation into the 68%, 95% and 99.7% intervals.
- Expected Value CalculatorExpected value of a discrete outcome list.
- Exponential Distribution CalculatorPDF, CDF and survival probability from rate λ.
- F-Test CalculatorCompare two variances with F, df and the p-value.
- Five Number Summary CalculatorMin, Q1, median, Q3 and max in one pass.
- Geometric Distribution CalculatorProbability that the first success lands on trial k.
- Hypergeometric Distribution CalculatorDraws without replacement — cards, lotteries, quality samples.
- Interquartile Range CalculatorIQR, quartiles and outlier fences.
- Linear Regression CalculatorBest fit line for paired data.
- Lottery Odds CalculatorOdds of matching all numbers in a lottery draw.
- Margin of Error CalculatorThe ± figure behind any poll or survey result.
- Mean Absolute Deviation CalculatorAverage distance from the mean, in the original units.
- Negative Binomial Distribution CalculatorProbability of the rth success on the nth trial.
- Normal Distribution CalculatorProbabilities under the bell curve.
- Normal Distribution Probability CalculatorP(X<x), P(X>x) and P(a<X<b) for a normal distribution.
- Odds Ratio Calculator2×2 table to odds ratio with a confidence interval.
- One Sample T-Test CalculatorTest a sample mean against a known or hypothesised value.
- Outlier CalculatorIQR fences and z-scores flag unusual points instantly.
- Paired T-Test CalculatorBefore-and-after comparison with t, df, p-value and effect size.
- Percentile Rank CalculatorPercentile rank of a value within a dataset.
- Poisson Distribution CalculatorProbability of k events in an interval.
- Population vs Sample Variance CalculatorCompare population and sample variance/standard deviation for a dataset.
- Probability CalculatorCombined probability of independent events.
- Quartile CalculatorQ1, median, Q3 and five number summary.
- Relative Risk CalculatorRisk ratio, absolute risk reduction and number needed to treat.
- Residual CalculatorObserved minus predicted, with standardised residuals.
- Sample Size CalculatorHow many responses you need for a reliable survey.
- Sample Size Calculator for a ProportionRequired sample size to estimate a proportion within a margin of error.
- Sensitivity and Specificity CalculatorFull diagnostic accuracy panel from four counts.
- Skewness CalculatorMeasure the lean of a distribution, left or right.
- Spearman Correlation CalculatorRank correlation for ordinal or non-linear data.
- Standard Deviation CalculatorSample and population spread, variance and standard error.
- Standard Error of the Mean CalculatorStandard error from sample standard deviation and size.
- T Test CalculatorOne-sample and two-sample t statistics.
- Trimmed Mean CalculatorDrop the extremes and average what's left.
- Two Sample T-Test CalculatorCompare two independent groups with Welch's t-test.
- Uniform Distribution CalculatorProbability, mean and variance for a continuous uniform.
- Variance CalculatorSample and population variance.
- Weighted Average CalculatorAverages where some values count more than others.
- Weighted Mean CalculatorAverages where some values count more than others.
- Z-Score CalculatorStandard score, percentile and tail probabilities.
- Z-Test CalculatorOne-sample z-test with p-value and confidence interval.
- Z-Test for a Single Proportion CalculatorTest a sample proportion against a hypothesized value.
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