English language

G*Power 3 covers statistical power analyses for many different statistical tests of the
* F test,
* t test,
* χ2-test and
* z test families and some
* exact tests.
G*Power 3 offers five different types of statistical power analysis:
* A priori (sample size N is computed as a function of power level 1-β, significance level α, and the to-be-detected population effect size)
* Compromise (both α and 1-β are computed as functions of effect size, N, and an error probability ratio q = β/α)
* Criterion (α and the associated decision criterion are computed as a function of 1-β, the effect size, and N)
* Post-hoc (1-β is computed as a function of α, the population effect size, and N)
* Sensitivity (population effect size is computed as a function of α, 1-β, and N)
G*Power 3 provides improved effect size calculators and graphics options. It supports both a distribution-based and a design-based input mode.
G*Power 3 is available for Mac OS X 10.4 and Windows XP/Vista.
G*Power 3 is free.

R is a language and environment for statistical computing and graphics. It is a GNU project. R provides a wide variety of statistical (linear and nonlinear modelling, classical statistical tests, time-series analysis, classification, clustering, ...) and graphical techniques, and is highly extensible. One of R's strengths is the ease with which well-designed publication-quality plots can be produced, including mathematical symbols and formulae where needed.
R is available in many different languages.

The Research Methods Knowledge Base is a comprehensive web-based textbook that addresses all of the topics in a typical introductory undergraduate or graduate course in social research methods. It covers the entire research process including: formulating research questions; sampling (probability and nonprobability); measurement (surveys, scaling, qualitative, unobtrusive); research design (experimental and quasi-experimental); data analysis; and, writing the research paper. It also addresses the major theoretical and philosophical underpinnings of research including: the idea of validity in research; reliability of measures; and ethics. The Knowledge Base was designed to be different from the many typical commercially-available research methods texts. It uses an informal, conversational style to engage both the newcomer and the more experienced student of research. It is a fully hyperlinked text that can be integrated easily into an existing course structure or used as a sourcebook for the experienced researcher who simply wants to browse.

This site has been prepared specifically for beginning researchers in developing countries. It is based on a book by the same title published by The Ahfad University for Women. They have created this Web site to make the contents of Methods for Social Researchers in Developing Countries available free to researchers in developing countries, where books are too expensive for faculty, students, or even for libraries to buy. Of course, they hope this site may be useful to researchers in other areas of the world as well. All material on this site may be freely downloaded or copied. The site has five main parts. Part 1, "Thinking Like a Researcher," introduces you to social research and the way researchers look at the world around them. Part 2 describes what you need to know to plan a research project. In Part 3 you will learn about ways of collecting data. Ways of analyzing data are described in Part 4. The last step in a research project — presenting your results — is covered in Part 5.