Statistics and Probability

This website provides training and tools to help you solve statistics problems quickly, easily, and accurately - without having to ask anyone for help.

Online Tutorials

Learn at your own pace. Free online tutorials cover statistics, probability, regression, analysis of variance, survey sampling, and matrix algebra - all explained in plain English.

Advanced Placement (AP) Statistics. Full coverage of the AP Statistics curriculum.
Probability. Fundamentals of probability. Clear explanations with pages of solved problems.
Linear Regression. Regression analysis with one or more independent variables.
ANOVA. Analysis of variance made easy. How to collect, analyze, and interpret data.
Survey Sampling. How to conduct a statistical survey and analyze survey data.
Matrix Algebra. Easy-to-understand introduction to matrix algebra.

Practice and review questions reinforce key points. Online calculators take the drudgery out of computation. Perfect for self-study.

AP Statistics

Here is your blueprint for test success on the AP Statistics exam.

AP Tutorial: Study our free, AP statistics tutorial to improve your skills in all test areas.
Practice exam: Test your understanding of key topics, through sample problems with detailed solutions.

Be prepared. Get the score that you want on the AP Statistics test.

Random Number Generator

Produce a list of random numbers, based on your specifications.

Control list size (generate up to 10,000 random numbers).
Specify the range of values that appear in your list.
Permit or prevent duplicate entries.

Free and easy to use.

Random number generator

Sample Size Calculator

Create powerful, cost-effective survey sampling plans.

Find the optimum design (most precision, least cost).
See how sample size affects cost and precision.
Compare different survey sampling methods.
Assess statistical power and Type II errors.

Tailor your sampling plan to your research needs.

Sample Size Calculator

Stat Toolbox

Check out our statistical tables and online calculators - fast, accurate, and user-friendly.

Discrete probability distributions

Continuous probability distributions

Special-purpose calculators

Each calculator features clear instructions, answers to frequently-asked questions, and a one or more problems with solutions to illustrate calculator use.

Acknowledgments

We wish to express our appreciation to those who assisted in the development of this website. We are particularly grateful to the following folks.

Many thanks to Peter J. Acklam, who wrote the algorithm for the Normal distribution, which you can view through the Wayback Machine at: Acklam algorithm.
We are also grateful to Geoffrey C. Barnes, Ph.D, who wrote a helpful VB.Net implementation of the Acklam algorithm, which is available through the Wayback Machine at: Barnes VB implementation.
A big tip of the hat to Justus Randolph for discovering and helping to correct an annoying bug in the Stat Trek code.
We are indebted to Ian Smith for alerting us to a problem with the chi square calculator and for his practical suggestions to fix the problem.
We are grateful to Chris Headlee, a math teacher at Marion Senior High School in Virginia, for thoughtful feedback that greatly improved our discussion of the negative binomial.
And finally, thanks to James Ulatowski of Mercedes, Texas for providing invaluable technical review which uncovered many mistakes and omissions.

Note: AP and Advanced Placement Program are registered trademarks of the College Board, which was not involved in the production of, and does not endorse this website.