I know, it's a "duh" statement. Lemme explain.
There are two sources of data I'm using here. One is the infamous Pew religious knowledge survey, the other is a recent Gallup poll that asked respondents how important religion is in their daily life and how often they attend services. Two different surveys, two different methodologies, but still it's fun to compare them. Each breaks down respondents into their religious affiliation (scroll down a bit to find this).
The winner in both knowledge and religiosity? Mormons. They finish a close third on knowledge to atheists (yes, irony alert, and I've written about this before) and Jews. Mormons easily win the importance/attendance contest.
Some of the categories don't easily compare. The Pew study, for example, breaks Protestants down into various categories. Gallup does not. If we collapse these into simpler categories for an equal comparison, though, you get the following:
Also, some of the differences above are modest. For example, on knowledge, the difference between Jews and Mormons is not statistically significant, so take the rankings with a grain of salt.
But the results do suggest the obvious -- that for people who see religion as important in their daily lives, they tend to do better on questions about religion. Yes, a "duh" moment, but it tells us something about the nature of knowledge and how there are pools of people out there who are knowledgeable about the stuff that matters to them rather than what matters to political scientists.