Crunch Your Numbers for Free

Practically every scientist uses statistics--from pharmacologists employing regression to understand the relation between the dose of a drug and its effects in the body, to agronomists using analysis of variance to test which fertilizer makes crops grow fastest. Thanks to VassarStats, created by psychologist Richard Lowry of Vassar College in Poughkeepsie, New York, anyone can now use the most popular statistical tests to analyze their data--free of charge.

Lowry began building Internet-based stats programs back in 1988 after growing "annoyed" with the cost of commercial software. His site offers an easy-to-use statistical package with bread-and-butter procedures such as linear regression, one-way and two-way analysis of variance, and the Mann-Whitney, chi-square, and t tests--as well as some more unusual procedures. Users can type in numbers or import data from a spreadsheet. The site also features simulations and demonstrations to teach statistical principles.

Indeed, Lowry strives to demystify the "magic rituals" behind the process. Instead of simply displaying a final P value--the odds of getting a significant result by chance if the experiment were repeated many times--the output includes intermediate results and offers cautions about possible misinterpretations. To find out more, novices and experts alike can page through Lowry's lucid 17-chapter Web textbook.