In statistics, analysis of variance (ANOVA) is a collection of
statistical models used to distinguish between an observed variance in a
particular variable and its component parts. In its simplest form, ANOVA
provides a statistical test of whether or not the means of several
groups are all equal, and therefore generalizes a test between these
groups. One test often used by statisticians and researchers in their
work is the Two-Way ANOVA, which determines the differences--and
possible interactions--when variables are presented from the perspective
of two or more categories. When a Two-Way ANOVA is implemented, it
enables one to compare and contrast variables resulting from independent
or joint actions. This brief provides guidance on how R can be used to
facilitate Two-Way ANOVA for data analysis and graphical presentation.
Along with instruction on the use of R and R syntax associated with
Two-Way ANOVA, this brief will also reinforce the use of descriptive
statistics and graphical figures to complement outcomes from parametric
Two-Way ANOVA.