ABSTRACT
This chapter discusses the statistical methods focused on assessing whether a set of groups, on average, differ on an outcome variable. To understand the sources of variation and what they quantify, it is worth discussing how you can partition the measurements on an outcome variable into these sources of variation. The independent groups t test using the pooled variance approach will give the same result as analysis of variance assuming equality of variance, because they are mathematically equivalent tests. The goal of analysis of variance is to determine if two or more groups differ from each other on some outcome variable on average, where the average is defined as the arithmetic mean. When conducting any study and readers have measured two or more groups on some outcome variable, there is almost certainly going to be some difference between the group means.
