Getting started with the pwr package
A simple example | More on effect size | More examples | pwr.2p.test - two-sample test for proportions | pwr.2p2n.test - two-sample test for proportions, unequal sample sizes | pwr.t.test - one-sample and two-sample t tests for means | pwr.t2n.test - two-sample t test for means, unequal sample sizes | pwr.chisq.test - Goodness of fit test | pwr.chisq.test - test of association | pwr.r.test - correlation test | pwr.anova.test - balanced one-way analysis of variance tests | pwr.f2.test - test for the general linear model | References and Further Reading