Lesson 9: EXPERIMENTAL DESIGN AND THE VARIANCE
Deviations about the mean of a population is the basis for most of the Statisticsal tests we will learn. Since we are measuring how widely a set of scores is dispersed about the mean we are measuring variability. We can calculate the deviations about the mean, and express it as variance or standard deviation. It is very important to have a firm grasp of this concept because it will be a central concept throughout the course.