Interpreting Main Effecs & Interactions in ANOVAs

Below are some blogs related to the question of interactions in ANOVA.  They might not be super-accessible for ‘yins – they are mostly discussions among well practiced stats users and not attempts to explain the issue in general terms.  One thing I think is apparent though is that I think the problem is not well defined – when someone says “how do you interpret interactions” different people think of it in terms of experiments analyzed with an ANOVA with only categorical variables, while others think in terms of regression with interactions between two continuous variables, or between a continuous and categorical variable.  I also think some people think in terms of how you interpret the result of an ANOVA table (which basically just tells you p-values) and interpretation of the means and other parameters you can get from your model.


Dynamic Ecology: Interpreting ANOVA interactions and model selection: a summary of current practices and some recommendations (also see the comments on their Poll: How do you interpret two-way ANOVAs?)

Andrew Gelman: Main effects and interactions

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