Hello everyone,

I am running a mixed effects model where I have two fixed factors, one with
2 levels and one with 4, and their interaction. Let's say these are my
factors and their levels:

FirstFactor: 1, 2
SecondFactor: A, B, C, D

For the interaction, I am interested in the four two-way comparisons, not
the two four-way comparisons. In other words, I want to test whether 1A is
significantly different than 2A, whether 1B is significantly different than
1B, etc; I am not interested in the comparison of 1A~1B~1C~1D.

However, the latter comparisons are what the coefficients seem to give me
when I summarize my model. For instance, the coefficient for the
interaction term "FirstFactor2:SecondFactorB" doesn't tell me how different
2B is from 1B, it tells me how different 2B is from 2A.

Is there a straightforward way to code the contrasts so that the
coefficients I get for the interaction terms do the comparisons I'm
interested in?

Thank you for your advice,
Steve Politzer-Ahles

-- 
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://www.linguistics.ku.edu/

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