Americans are by all measures a deeply religious people, but they are also deeply ignorant about religion.

Researchers from the independent Pew Forum on Religion and Public Life phoned more than 3,400 Americans and asked them 32 questions about the Bible, Christianity and other world religions, famous religious figures and the constitutional principles governing religion in public life.

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.