ABSTRACT
In the previous chapter we examined t-tests, which look for group differences when there are only two groups. Although it was not framed this way when talking about t-tests, essentially we had one variable that was independent and measured categorically (the group splitting factor) while we had another that was dependent and measured on an interval or continuous scale (the measurement we took from the groups). When we want to ask the same question of whether the groups come from the same or different populations but we have more than two groups, we will use a one-way analysis of variance (ANOVA). For example, in this chapter we will look at the question of whether groups who differed in the kind of time they got to plan and write an essay performed differently on an evaluation of that essay. In this case there is one dependent variable, which is the evaluation of the essay, and one independent variable, which is group membership. In Ellis and Yuan’s study (2004) there were three different levels of planning/writing time, so we cannot use a t-test; we must use a one-way ANOVA.
