Most philosophers are atheist.

[Jehanne]

There are, of course, only so many philosophers in the World today.  If their survey was not a census, then it was at least a quorum.

I did work in Statistical Process Control for 14 years, have a MBA from a major university, etc.

I dont know why I'm pretending to be an authority on the matter. Common syndrome on the internet but not one I've gotten. I blame hospital drugs and whathaveyou.

It isn't complex -- if a census is possible and economical, then take a census.  If a sample is only possible (e.g., "blood draw", and as an aside note, if you meet someone who doesn't believe in statistical sampling, advise them to tell the lab tech that, "I don't believe in statistical sampling, and so, 'take it all'" for their next labs), then one has no choice but to sample.  Still, it is often the difference between tasting from a large pot versus a smaller one; often, the same-sized spoon does the job just as well.  With 3K philosophers out of what, 10K at most, the sample, even if it was not random, was probably thoroughly representative.  If not, one would have expected some sort of blow-black from the "believing" contingency of philosophers.  Even Francis Collins admits that most of his colleagues within the National Academy of Sciences are atheistic, and the response rate for that survey was only 50%; in fact, it is more likely than not that the believing NAS members were more likely to respond than the non-believing ones, for that latter really did not have much of a motive to do so!