Compare groups means tutorial

Learn how to test for a difference between the means of 2 groups and estimate the size of the effect.

Twenty-one African-American men participated in an experiment to test whether increasing calcium intake reduces blood pressure. Ten of the men took a calcium supplement for 12 weeks while the remaining 11 men received a placebo. Researchers measured the blood pressure of each subject before and after the 12-week period. The experiment was double-blind.

In this tutorial you will perform the following tasks:

1. Testing for a difference of means
   Test the hypothesis that the means of the groups are equal.
2. Testing assumptions of the t-test
   Test the assumptions of the statistical procedure.
3. Trying a different statistical test
   Make a copy of the analysis and try a different statistical test.