In this section, Professor Ketterle discusses his use of clicker questions during lectures.
Using Clicker Questions to Encourage Participation
I use i>clicker™ software and hardware in this course. Specifically, I make use of clicker questions 
to encourage students to participate in class. Typically, there are some students, for various reasons, who are reluctant to raise their hands during lectures. Because clickers allow students to answer questions anonymously, more students tend to participate when I invite them to use clickers. Clickers are not in any way necessary for having engaging discussions, but they do get more students involved.
"The best clicker questions are seemingly easy and completely based on course materials—so students know that they should be able to answer them—but are formulated in a way that takes students out of their comfort zones."
The clicker technology also enables students to view a histogram of their collective responses to questions. Often, students have interesting reactions when they view the histograms. They are generally amazed by how everybody answered questions correctly—or by how nobody answered correctly. Interesting discussions are triggered when students realize that half the class has picked answer A, and half the class answer B.
Leveraging Clicker Questions to Push Students out of their Comfort Zones
I try not to ask clicker questions that are easily answered by everyone. These kinds of questions are too simple, and some students may find them boring. I prefer to ask questions about concepts students may not be grasping. Sometimes I’ve been surprised that there was a lack of understanding—and the clicker questions gave me an opportunity to explain the concepts from different angles. My advice to other educators is: if you’re in doubt about whether students understand what feels to you like a basic concept, ask a question about it; you may be surprised by how difficult students find the concept.
Questions that assess students’ understanding of course material are helpful, but the best clicker questions are seemingly easy and completely based on course materials—so students know they should be able to answer them—but are formulated in a way that takes students out of their comfort zones. They really have to think about these questions! They cannot just use simple analogies. I’ve often seen that with these questions, the histograms for the different answers are completely flat, which means the class has no clue as to how to answer these questions.
These clicker questions garner rapt attention from students because it becomes clear to individual students that not only they may have responded incorrectly, but also that the whole class got it wrong. They realize there must be something they should understand—that the question involves a concept that physicists misunderstand. They pay very close attention as I explain the concept again. So, yes, sometimes I try to find clicker questions that may confuse a lot of students, because making sense of our confusion is how we learn.
In particular, sometimes I purposely try to find clicker questions that look at the material from a different perspective. I try to use clicker questions to show students that they may have some knowledge about a specific aspect of a concept, but that they haven’t yet developed a sense of intuition about the concept as a whole. It’s this sense of intuition that is important for them to hone. An essential part of my teaching is encouraging students to not just think formulaically, but in more intuitive and comprehensive ways. And I do this, sometimes, through clicker questions.
Clicker Questions and Curricular Decisions
Although there’s very little overhead in preparing to use the clickers (I just take my box with the clickers to class), incorporating clicker questions into my lectures takes some class time. I’ve had to shorten some material and remove topics from the syllabus to make room for clicker questions. In light of these choices, I’ve regularly asked students if they like the clicker questions. They routinely respond positively and note they’d rather have more than fewer clicker questions. Given the nature of the material, I have considerably more clicker questions in 8.421 than in 8.422, but it’s a process. Every time I teach the course, I get some great additional ideas for clicker questions.
