Here is a list of some of the most useful statistics web sites we know of. We hope you agree.

Know of other great resources? Let us know.

Tutorials and General Information Related to Statistics and Data Analysis
Online Statistics Tools
Mediation and Moderation
Structural Equation Modeling (SEM)
Multilevel Modeling
Tools for Power Analysis

Tutorials and General Information Related to Statistics and Data Analysis

American Statistical Association (ASA)
ASA is a leading professional association for statistics and statisticians.

Econometrics Resources on the Internet
Many useful links to econometrics resources.

Rice Virtual Lab in Statistics
A comprehensive web site with information about a variety of statistical tests and helpful web-based demonstrations that help clarify statistical concepts.

A web site provided by the University of Washington that provides information on statistical and methodological issues in research, tutorials, etc.

Statistical Software Tutorials from the University of Texas
Very helpful tutorials on the use of many statistical packages, including AMOS, HLM, LISREL, Mplus, SAS, and SPSS.

StatLib: Data, Software and News from the Statistics Community
Lots of statistical software and data sets that are available for download.

Statnotes: Topics in Multivariate Analysis
Online notes for basic and advanced statistical techniques written by G. David Garson.

UCLA Statistical Computing Seminars
A large resource for statistics information with downloadable movies of seminars covering latent variable analysis, multilevel modeling, and longitudinal data analysis, as well as movies on specific software, including Mplus, Stata, SAS, SPSS, and R.

Online Statistics Tools

Critical Values (or alpha levels) for common statistical distributions
This page provides critical values for z, student t, F, and chi square distributions. You can also determine your alpha level for a given test statistic and degrees of freedom.

Critical Values for the Correlation Coefficient
This site quickly gives you the critical r value at .05 and .01 alpha levels for the degrees of freedom that you select.

Effect Size Calculator
Offers a variety of calculators for calculating d and r, written by Lee Becker.

Italassi Graphing Program
A freeware program that displays interactions in regression models and is able to read raw data from SPSS or .dat files.

R Project for Statistical Computing
R is a free software environment for statistics and graphics.
Kristopher Preacher's interactive calculators for several statistical techniques. Also lots of useful information, articles, and syntax

Mediation and Moderation

Andrew Hayes' SPSS and SAS Macros
Very useful and easily implemented SPSS and SAS code for relatively complex mediation and moderation models among others.

David Kenny's Mediation Page
Lots of easily-digested information about statistical mediation with links to other useful resources.

David Kenny's Moderation Page
Great introduction to statistical moderation.

David MacKinnon's Mediation Page
Lots of information, publications, and syntax related to statistical mediation.

Kristopher Preacher's Code for Mediation and Moderation
An assortment of progrmming code to conduct mediation and moderation in a variety of software packages.

Structural Equation Modeling (SEM)

David Kenny's Structural Equation Modeling Site
A good portal for information on structural equation modeling

Ed Rigdon's SEM FAQ
A variety of information relevant to basic SEM analyses.

Mplus Discussion Forum
Excellent information on many basic and advanced issues in SEM, moderated by the authors of Mplus software.

Multilevel Modeling

Joop Hox's Website
Lots of information about multilevel modeling, including a free version of Dr. Hox's 2002 book.

Multilevel Modeling Discussion List
Searchable archive and ongoing discussion on HLM analyses.

SSI Online Resources
Many resources relevant to HLM analyses provided by the authors of the HLM software package.

Tools for Power Analysis

G*Power is a free, general power analysis program that comes in versions for Windows XP/Vista and Mac OS X 10.4. Older versions are available that work with a wider variety of operating systems.

Java Applets for Power and Sample Size
Graphical a-priori power calculators for basic statistical analyses.

PINT - Two-Level Power Analysis
Tom Snijder's downloadable program, Power analysis IN Two-level designs (PINT).

Optimal Design - Multilevel Power Analysis
A flexible and easy-to-use power calculator for a variety of two- and three-level cross-sectional and longitudinal designs.