Apparently they asked questions about what’s in the Bible and the Mormons came out looking good. That’s cuz we actually read and study the Bible.
Actually, the survey was more on religion in general and didn't have much to do with the Bible at all.
Here is the quiz if you want to take it. I found it to be really easy (got 100%) and had very little to do with Bible knowledge.
http://features.pewforum.org/quiz/us-religious-knowledge/index.php