Just a few points:
1) I would not call atheism “rationality.” Atheism requires a certain degree of blind faith and accepting lack of evidence for religion as evidence of not-religion which is not in concordance with the principles of rationality. Perhaps “agnostic atheism” would be a more reasonable perspective. “There is a god” and “there is no god” are both non-falsifiable assertions, and I can think of few things that I would accept as corroborating evidence thereof. You cannot deduce atheism from the fact that religion does not seem to be correct. You can, however, reasonably state that while there might be a god, there probably is not.
2) Occam’s razor is not necessarily applicable sui generis. I would direct you to Elliott Sober’s excellent paper on the subject, “Let’s Razor Occam’s Razor.” It is a useful argument against the existence of a god, but certainly not definitive.
I took the survey! I also assumed the probabilities were meant to be first-glance intuitive. I wish I’d known people were actually doing research, for I would have done the calculations!