To be honest, I'm not very sure of what I want, myself. I have reason to believe that they'll consider it acceptable regardless of whether there's a control group or not (this being the CS department and not the psych one)
How about going to the office hours of a professor in the psychology department and ask them for advice on how to run your study?
Your question made me go d'oh, in that I suddenly remembered that there's an obvious place right nearby to ask help from, both for designing the study and recruiting test subjects. I'll talk with them, thanks.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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