I love psychological experiments. I can guarantee you that the 'experiment' was in the preface...
It said the 'test' would last no longer than 1 hour, the fact that most people would turn away at that point means you've eliminated the portion of the population that wou didn't want to test...
The question was mathematical, 2 bullets, 6 chambers, spin + miss by friend.... "Do you take gun and fire, or spin chamber first?" Well mathematically the answer is simple (but I wont give you my response)
On top of this you allow the participant to view 'other participant choices' - which really means you can tell them that 5 of 30 (in my case) chose one option, and then ask for feed back of if this affected your decision on the next page.
Not to mention the way you phrased your question on AB. I very much doubt you need 500 participants to meet your criteria for your assignment as results from psych experiments are always averaged/worked out from how ever many participants there are. - Though I'll admit, the science page on AB is a good way to recruit the demographic you wanted...
I think that's all - I'm trying to get the spot of 'Best Answer' and I've not got one yet :( - Maybe you can rectify that? :)
IHI