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Statistics

Distributions, hypothesis tests, and confidence intervals for any dataset.

21 tools

Standard Deviation

Mean, variance, and SD for any dataset.

P-Value Calculator

From a test statistic and distribution.

Confidence Interval

For a mean or proportion.

Z-Score Calculator

Standardize a value and find its percentile.

Normal Distribution

Probabilities under the bell curve.

T-Test Calculator

One- and two-sample tests with p-value.

Chi-Square Calculator

Goodness-of-fit from observed vs expected.

Correlation Calculator

Pearson's r, r², and significance.

Sample Size Calculator

Participants needed for a margin of error.

ANOVA Calculator

One-way analysis of variance, F-table.

Mean, Median, Mode

Mean, median, mode, range, and quartiles from a data set.

Linear Regression

Least-squares line, slope, intercept, and r².

Percentile Calculator

Percentile rank of a value, and value at a percentile.

Binomial & Poisson

Binomial and Poisson probabilities.

Probability Calculator

Single and combined event probabilities.

Effect Size Calculator

Cohen’s d effect size from two group means and standard deviations.

Margin of Error Calculator

Margin of error for a survey proportion at a confidence level.

Five-Number Summary

Min, Q1, median, Q3, max, IQR, and outliers with a box plot.

Weighted Mean Calculator

Weighted average from value and weight pairs.

Geometric Mean Calculator

Geometric mean of a set of positive numbers.

Coefficient of Variation

Relative variability — standard deviation as a percent of the mean.

About statistics tools

Compute the statistic, see the distribution, and understand what the number means — not just what it is.

When to use these tools

Common statistics tasks and the tool that handles each one.

Frequently asked questions

Common questions about statistics — the concepts behind the tools above.

What is the difference between mean, median, and mode?
The mean is the average, found by adding all values and dividing by how many there are. The median is the middle value when the data is sorted, and the mode is the value that occurs most often. The median is often more reliable than the mean when the data has outliers or is skewed.
What does standard deviation tell you?
Standard deviation measures how spread out data is around the mean, in the same units as the data. A small standard deviation means values cluster tightly near the average, while a large one means they are more scattered.
What does a p-value mean in plain terms?
A p-value is the probability of seeing a result at least as extreme as yours if the null hypothesis (no real effect) were true. A small p-value, commonly below 0.05, suggests the result is unlikely to be due to chance alone, but it does not measure how large or important the effect is.
Does correlation prove causation?
No. Correlation only means two variables tend to move together; it does not show that one causes the other. The link can be coincidental or driven by a third, hidden variable, so establishing cause usually requires a controlled experiment.

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