๐ Statistics & Probability
Free statistics calculators: descriptive stats, standard deviation, normal distribution, z and t tests, confidence intervals, p-values, probability and combinatorics.
From a column of numbers to a defensible conclusion: means, medians and deviations first, then z-scores, t-tests, p-values and confidence intervals that state the assumptions behind each result.
Probability and permutation/combination tools handle the counting side โ dice, draws, arrangements โ so homework and real data analysis share one consistent toolkit.
Confidence Interval Calculator
Compute a confidence interval for a population mean with Z or t critical values.
Normal Distribution Calculator
Compute cumulative probabilities, tail probabilities, interval probabilities for any normal distribution. Enter ฮผ and ฯ โ fully offline.
P-Value Calculator
Calculate the p-value from a Z-score (test statistic) for hypothesis testing. Supports left-tailed, right-tailed, and two-tailed tests with significance conclusions at alpha 0.05 and 0.01.
Permutation & Combination Calculator
Calculate permutations (nPr) and combinations (nCr) for any n and r values.
Probability Calculator
Calculate the probability of any single event.
Standard Deviation Calculator
Compute sample and population standard deviation, variance, and mean from your data.
Statistics Calculator
Compute mean, median, mode, standard deviation and more.
T-Test Calculator
Calculate one-sample and two-sample (Welch's) t-test statistics, degrees of freedom, p-values, and critical values.
Z-Score Calculator
Convert raw scores to z-scores and find percentile ranks, probability, and interpretation.
Frequently asked questions
Which standard deviation does the calculator return?
Both sample and population versions, clearly labeled, with the variance shown alongside.
Do the test calculators choose the test for me?
No โ they execute the test you select and state its assumptions; choosing between z, t and others stays a decision you make.
How are p-values computed?
From the test statistic under the stated distribution, with the alternative hypothesis (one- or two-sided) explicit in each result.