G*Power

Please note The next version, G*Power 3, is now available. You may still use G*Power 2, and in some cases you have to: If you still use MS-DOS or MacOS 7 to 9 as operating systems, you are limited to G*Power 2. For all others, G*Power 3 is highly recommended.

What is G*Power?

  

G*Power 2 is a general power analysis program that comes in two essentially equivalent versions: one runs under the Macintosh OS and the other was designed for MS-DOS.
   

What can it do?

  

G*Power 2 performs high-precision statistical power analyses for the most common statistical tests in behavioral research, that is,

  • t-tests (independent samples, correlations, and any other t-test),
  • F-tests (ANOVAS, multiple correlation and regression, and any other F-test), and
  • Chi2-tests (goodness of fit and contingency tables).

G*Power 2 computes

  • power values for given sample sizes, effect sizes, and alpha levels (post hoc power analyses),
  • sample sizes for given effect sizes, alpha levels, and power values (a priori power analyses), and
  • alpha and beta values for given sample sizes, effect sizes, and beta/alpha ratios (compromise power analyses).

The program may be used to display graphically the relation between any two of the relevant variables and it offers the opportunity to compute the effect size measures from basic parameters defining the alternative hypothesis.

A description of the program and the relevant background is published in

Erdfelder, E., Faul, F., & Buchner, A. (1996). GPOWER: A general power analysis program. Behavior Research Methods, Instruments, & Computers, 28, 1-11.
 

Price

  

G*Power 2 is free. You may give the program to friends and colleagues who might find it useful. However, if you want to include G*Power on a shareware or freeware CD-ROM, or if you want to distribute it together with commercial software, you must ask the authors for permission. Please contact Axel Buchner, Franz Faul, or Edgar Erdfelder.
   

Download

  

Macintosh version (Version 2.1.2 for 68K and PowerMacs) of G*Power (330 K)

International MS-DOS version of G*Power (350 K, updated May 15, 1998)

German MS-DOS version of G*Power (450 K, updated May 15, 1998).

GP-Setup.exe (800 K), a setup procedure which will install G*Power on machines with a Windows-based operating system. We are grateful to

Dr Grant Devilly
Department of Criminology
University of Melbourne
Parkville, Victoria 3010
Australia

for developing an contributing GP-Setup.
   

Help

  

The guide to G*Power is just one click away.
   

Register

  

We encourage you to let us know your e-mail address. As a registered user, you will be informed about future program revisions. Your e-mail address will be used for this purpose only.

To register now, join the G*Power mailing list.
   

Acknowledgements

  

Here is a list of the people who were very helpful in developing G*Power and the guide to G*Power.