Question

What are the two main reasons for including covariates in anova?

Answer 1

Answer:

Variance from both types of variables are accounted for in a linear model (e.g., regression, ANCOVA). So, a covariate is not just a third variable not directly related to the dependent variable. It is merely a dimensional variable. ... For example, a factor may allow contrasts between groups, while a covariate would not.

Answer 2

Answer:

Explanation:

So, a covariate is not just a third variable not directly related to the dependent variable. It is merely a dimensional variable.