What do to with multi-arm trials?

[acoppock]

There's a couple of analysis choices to worry about:

1. Which comparisons to report (all pairwise? all versus some control condition?)
2. Which multiple comparisons correction to employ? Holm? RI? Some comparisons are in the same "family" some are not.
3. Do multi-arm trials change how we think about covariate adjustment?
4. When/how are we allowed to collapse over conditions?
5. When/how are we allowed to parameterize (e.g., in Guess and Coppock, we code conditions for their "information content" and estimate a linear model)