watch late-night comedy...stay politically informed?

As reported in this story, according to the University of Pennsylvania’s National Annenberg Election Survey, those who watch late-night comedy shows are more knowledgable about politics than those who do not:

Polling conducted between July 15 and Sept. 19 among 19,013 adults showed that on a six-item political knowledge test people who did not watch any late-night comedy programs in the past week answered 2.62 items correctly, while viewers of Late Night with David Letterman on CBS answered 2.91, viewers of The Tonight Show with Jay Leno answered 2.95, and viewers of The Daily Show with Jon Stewart answered 3.59 items correctly. That meant there was a difference of 16 percentage points between Daily Show viewers and people who did not watch any late-night programming

Keep in mind that things that coincide do not necessarily imply causation. In other words, the survey provides no answers to these questions:

• Does watching late-night comedy cause you to become more knowledgeable?
• Does being more knowledgeable make you want to watch more late-night comedy?
• Do these two characteristics just happen to coincide in people, each of them perhaps caused by something else completely?

And remember that "cause and consequence" is one of the common sources of argument in the rhetorical appeal of logos.

Update:Check out what Andy Cline has to say.