Statistics, Probability, and Survey Sampling

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

Stack of books topped by an apple

Teach Yourself Statistics Online

Learn at your own pace. Free statistics tutorials cover statistics, probability, and survey sampling - all explained in plain English.

How to Prepare for AP Statistics

AP Tutorial: Read our free, AP statistics tutorial to improve your skills in all test areas. > Learn more
Practice exam: Test your understanding of key topics, through sample problems with detailed solutions. > Learn more
Study guide: Read our review of the most popular AP study guides, and choose the right guide for you. > Learn more
Calculator: Compare AP-approved graphing calculators, based on price and user ratings. > Learn more

Analytical Tools

Random numbers

Random Number Generator

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

  • Control list size (generate up to 1000 numbers).
  • Specify the range of values that appear in your list.
  • Permit or prevent duplicate entries.

Free and easy to use. > Learn more

Sample Planning Wizard

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. > Learn more

Wizard hat

Probability Calculators


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

  • Many thanks to Peter J. Acklam, who wrote the algorithm for the Normal distribution. He has generously shared that algorithm, which you can access at:

  • We are also grateful to Geoffrey C. Barnes, Ph.D, who wrote a helpful VB.Net implementation of the Acklam algorithm.

  • 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.

*   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 web site.