The dropdowns for the answer choices are kinda clunky. It'd be even better if you had radio buttons or could just type them in.
Edit: I take it back. You can select the first box, then just type the letters and hit tab for each one. That's actually pretty easy to use.
I like the graphs, but I'd split up some of your categories:
Principle questions split into "principle conform" and "principle justify"
Parallel questions split into "parallel reasoning" and "parallel flaw" and "parallel principle"
Inference questions split into "must be true" and "most strongly supported."
Also, we shouldn't have to give an email address if we uncheck the "add me to the PencilNerd mailing list" box, IMHO.