One-Way and Factorial Analysis of Variance

Analysis of variance (ANOVA) is a statistical procedure that can be used to compare mean differences between three or more groups. This chapter presents the application of fixed-effects ANOVA using a situation where school-age students have been assigned to three different technology-assisted reading programs. The school wants to know if the programs help develop students’ reading comprehension ability. How might one determine whether students in these groups differed on a reading comprehension posttest? In this chapter, I demonstrate how a one-way ANOVA can be applied to determine whether the effect of reading program assignment (as a categorical independent variable) is meaningful in explaining the reading comprehension outcome (as a continuous dependent variable). I describe how to test statistical assumptions, and how to report the results in narrative and graphical format. I also demonstrate the use of factorial ANOVA by adding a second independent variable, Trait Status, with two levels (“High” and “Low”). I demonstrate how to evaluate the main effects of Reading Program and Trait, while also paying special attention to the interaction between Trait status and Reading Program. Finally, I discuss how ANOVA can be applied to answer questions related to educational technology.