describe thedifference betweenbetween-treatments(groups) andwithin-treatments(groups) variations. Explain how to evaluate the variation and other methods to ensure that thedata are appropriate to use for the test. Illustrate ideas using a specificexample.

• What kind of test requires this between/within distinction?
• What kind of variance do we want more of and what kind of variance do we want less of?
• Why? How do these kinds of variance relate back to null hypothesis testing and our ability to reject the null?