Statistics Calculators

Calculate sample or population standard deviation and variance, with every intermediate step shown and the choice of divisor explained.

Convert a raw value to a z-score and probability, find the value at a target percentile, or find the probability between two z-scores.

Calculate binomial probabilities — exactly k, at most k, at least k — plus the mean, variance and standard deviation.

Calculate Poisson probabilities for a given rate and count, with exact, cumulative and tail probabilities, and a full distribution table.

Calculate the number of permutations or combinations of r items chosen from n, with and without repetition, and the full factorial.

Calculate the probability of two events with AND, OR and NOT, a series of repeated independent events, or the probability of a normal distribution falling between two bounds.

Calculate a confidence interval for a sample mean or proportion, with the margin of error and what the confidence level actually means.

Work out how large a survey sample needs to be for a target margin of error, or find the margin of error a given sample size already produces — with a finite-population correction.

Calculate a p-value from a Z or T test statistic, for one-tailed or two-tailed hypothesis tests.

Calculate a golf Handicap Index from recent rounds, using score differentials and the World Handicap System's best-rounds averaging.

Fit a least-squares line to paired data — slope, intercept, correlation coefficient r, R², and a prediction for any x.

Run a chi-square goodness-of-fit or independence test — the statistic, degrees of freedom, p-value and the decision at your significance level.