ANOVA for unbalanced data: an overview

When the response variables have continuous distributions and the conditions are discrete, whether inherently or by design, then it is appropriate to analyze the data using analysis of variance (ANOVA). When data conform to a complete, balanced design (equal numbers of observations in each experimental treatment), it is straightforward to conduct an ANOVA. This paper provides an overview of the consequences of lack of balance and gives some guidelines to analyzing unbalanced data for models involving fixed effects. -from Authors