- t Test for Independent Samples Calculator
This site allows you to paste in your own data and perform a t test for independent samples. Paste data from each sample in the two upper boxes and select "t Test of independent data sets (two samples, two-tailed)" and then press "Go." You'll see the t score, the degrees of freedom, the sample means, and the resulting p value. As an experiment, try analyzing the same set of data as a t test for independent samples and then as a t test for dependent samples. What does the result suggest about which test has more power?
- William Sealey Gosset (1867-1937): Brewer, Statistician
Read a short biography of William Sealey Gosset, the man who invented the t distribution and the t test while working for the Guinness Brewery in England. Because Guinness prohibited its employees from publishing any papers, Gosset published his work under the pseudonym "Student."
- Online t Table
In case you don't have your textbook handy, here is site that has a t table for p values .10, .05, .025, and .01, up to 100 degrees of freedom.
- Exact p-value Calculator
Ever want to know the exact p associated with a t value you've computed? This site has a worksheet that allows you to enter your t and degrees of freedom. Click the "Calc P" button and get an exact p-value. (The same worksheet will also compute the t if you have the p and the df.)
- Minnesota Twin Family Study
The Minnesota Twin Registry is a research initiative based at the University of Minnesota that seeks to identify the genetic and environmental influences on the development of various psychological traits. In order to accomplish this, the researchers compare identical (MZ) twins with fraternal (DZ) twins. Both types of twins usually share very similar environments but they differ in their genetic relatedness: MZ twins are genetic duplicates whereas DZ twins share 50% of their genes. This research involves a two-sample research design that requires statistical analyses such as a t test for independent samples. For more information about the findings to emerge from this technique, clink on the link for "What's Special About Twins to Science?"
- Physicians' Reactions to Patient Size: An Example of a Study that Used a t Test for Independent Means
Find out about an interesting real study that used a t test for independent means. Don't worry if you don't understand every single statistic presented (such as the box plots), simply concentrate on the t test.
