According to a University of Maryland study:
Those who receive most of their news from Fox News are more likely than average to have misperceptions. Those who received most of their news from NPR or PBS are less likely to have misperceptions. These variations cannot simply be explained as a result of differences in the demographic characteristics of each audience, because these variations can also be found when comparing demographic subgroups of each audience
The study found that:
23% of the people who got their news from NPR or PBS were misinformed about the Iraqi War (for example, they believed that "most of the world" supported the U.S.-led invasion of Iraq)
55% of the people who got their news from CNN were misinformed.
80% of the people who got their news from Fox were misinformed.
The interesting stats come in when you factor out people’s political leanings. For example:
78% of Bush supporters who get their news from Fox were misinformed
whereas . . .
Only 50% of Bush supporters who get their news from PBS or NPR were misinformed.
The full study can be read here