ANOVA, or "analysis of variance", is a fun way to compare the means of three or more samples. Since you've been doing hypothesis testing of means for a while now, this video is pretty quick. First I walk you through the null and alternative hypotheses for this type of problem, then I show you how easy it is to crank out on your calculator.
If you do not have an account, you should get one, because it is awesome! You can save a playlist for each test or each chapter, and save your "greatest hits" into a "watch right before the final" list (not that we recommend cramming, but when in Rome...)