On average, people who took the survey answered half the questions incorrectly, and many flubbed even questions about their own faith.
Those who scored the highest were atheists and agnostics, as well as two religious minorities: Jews and Mormons. The results were the same even after the researchers controlled for factors like age and racial differences.
So Mormons did almost as well as atheists? That makes sense. I knew a bit about religion as a Mormon. Then when I learned a little bit more, I became an atheist.
Oh, and in fairness, I did score 15 out of 15 on the poll, but the last question was a 50/50 lucky guess.