Math and Statistics

A/B conversion test: rates, relative lift, two-proportion z-test p-value, confidence interval and a significance verdict.

Exact counts: factorial, combinations, permutations, with repetition, derangements and Catalan numbers, as big integers.

Confidence interval for a mean (t interval from a list) or a proportion (Wilson and Wald from successes and trials).

Pearson and Spearman correlation of two lists with p-values, plus the least-squares line, R squared and an optional prediction.

Probability density or mass, cumulative probability and quantiles for normal, binomial, Poisson and Student t distributions.

Greatest common divisor, least common multiple, Bezout coefficients and modular inverse for integers of any size.

Primality test and prime factorization of integers up to 10^19, with divisor count, divisor sum, Euler totient and number type.

Required sample size for a survey (margin of error, optional finite population) or an A/B test (baseline, lift, power).

Descriptive statistics for a list of numbers: mean, median, mode, spread, quartiles, outliers, skewness and kurtosis.

Welch two-sample or one-sample t-test: t statistic, degrees of freedom, p-value, confidence interval and Cohen's d.