Good question; we've been working on writing up a research paper comparing raising hands and using clickers, and other work has been done on this too. Briefly, having students raise their hands to vote for an answer is really different than using clickers - in almost all cases you'll get a completely different response from students.

When students vote with clickers, they know it is publically anonymous (the rest of the class and the instructor doesn't know how each student votes), their votes are recorded (usually for some course credit), and the aggregate student responses are instantly and accurately counted. These three features together really make a huge positive difference: students are much more likely to vote honestly, vote in high numbers,  commit to an answer, and be vested in the outcome of the questioning process (and the answer!) when using clickers. We found that students who voted by raising hands were much more likely to focus on the majority answer and vote with it, they had little motivation to vote at all as they did not receive any credit for doing so, and they found questions less useful for their learning (even when they were identical to those the clicker group). Instructors have to take time to try to estimate the number of votes manually, and the student votes they did get were not representative of student thinking, so the questions usually didn't help the instructor know where students were at. 

Certainly the pedagogical approach used makes a big difference - but the technology of clickers sets up a classroom environment conducive for student engagment and learning, and it's difficult to see how voting by raising hands or using colored cards could also include the same conditions of public anonymity, private accountability, and instant and accurate feedback.

Hope that helps answer your question,

Andrea

Dr. Andrea Bair

Dept. Geological Sciences, University of Colorado

Clickers are MUCH better than raised hands, because of the anonymity.

Compared to colored cards, this depends much more on how good YOU are as teacher.

If you convince students that discussion with their peers is a vital part of improving

their grades, using cards to collect the answers should be as good as clickers.

However, practical experience shows that recording repsonses with clickers and

making this a small amount of the class grade almost always improves participation

and attendance.  I'm quite a dynamic lecturer (used to be on NPR...), but I use clickers

rather than cards because our student interviews tell us a significant number

of students think clickers improve their attendance as well as their attention in class.

There is more accountability with clickers.  Also, you have all the data in case you

want to do research.