Python Data Analysis Cookbook

Evaluating relations between variables with ANOVA

Analysis of variance (ANOVA) is a statistical data analysis method invented by statistician Ronald Fisher. This method partitions data of a continuous variable using the values of one or more corresponding categorical variables to analyze variance. ANOVA is a form of linear modeling. If we are modeling with one categorical variable, we speak of one-way ANOVA. In this recipe, we will use two categorical variables so we have two-way ANOVA. In two-way ANOVA, we create a contingency table—a table containing counts for all combinations of the two categorical variables (we will see a contingency table example soon). The linear model is then given by the equation:

This is an additive model where μ_ij