Analysis of Variance (ANOVA) in R: One-Way and Two-Way ANOVA

This chapter provides the users with information on how to conduct Analysis of variance (ANOVA)Analysis of Variance (ANOVA) test in R. This test helps to determine the mean differences that may exist in data samples. The most common types of the test, namely—One-way and Two-way ANOVATwo-way ANOVA are explained and practically illustrated in R by the authors in this chapter. Whilst the One-way ANOVAOne-way ANOVA is used to compare the differences in meanDifference in mean between one independent (categoricalCategorical or ordinal) variable and one dependent (continuousContinuous) variable, whereby the independent variable must have at least three levels or categories, i.e., a minimum of three different groups of a specified variable or groups. On the other hand, the Two-way ANOVA is used to compare the differences in meanDifference in mean between two independent (categoricalCategorical or ordinal) variables (with three or more multilevel) and one dependent (continuousContinuous) variable. In summary, the ANOVA test is used for examining the effects that one or two or even multiple factorsMultiple factors (independent variables) have on the population of the study (usually continuousContinuous dependent variable) simultaneously or all at the same time.