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.

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


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

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.
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Create powerful, costeffective 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.
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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:
http://home.online.no/~pjacklam/notes/invnorm.
 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. 