Category: astro 101

Peer instruction is worth the effort

Most blog posts, articles or books with a title like this would go on to describe the positive impact of peer instruction on student learning. I even write those kinds of posts, myself.

This one is different, though, because it’s not about peer instruction being worth the effort by (and for) the students. This one is about how it’s worth the effort by (and for) the instructor.

In my job with the Carl Wieman Science Education Initiative, I sometimes work closely with one instructor for an entire 4-month term, helping to transform a traditional (read, “lecture”) science classes into productive, learner-centered environments. One of the common features of these transformations is the introduction and then effective implementation of peer instruction. At UBC, we happen to use i>clickers to do facilitate this but the technology does not define the pedagogy.

Early in the transformation, my CWSEI colleagues and I have to convince the instructor that they should be using peer instruction. A common response is,

I hear that good clickers questions take soooo much time to prepare. I just don’ t have that time to spend.

So, is that true, or is it a common misconception that we need to dispel?

Here’s my honest answer: Yes, transforming your instructor-centered lectures into interactive, student-centered classes takes considerable effort. It feels just like teaching a new course using the previous instructor’s deck of ppt slides.

What about the second time you teach it, though?

A year ago, in September 2010, I was embedded in an introductory astronomy course. The instructor and I put in the effort, her a lot more than me, to transform the course. By December, we were exhausted. Today, one year later, she’s teaching the same course.

My, what a difference a year can make.

This morning I asked her to tell me about how much time she spends preparing her classes this term, compared to last year. We’re not talking about making up homework assignments or exams or answering email or debugging the course management system or… Just the time spent getting ready for class. This year she spends about 1 hour preparing for her 1-hour classes. That prep time consists of

  • a lot of re-paginating last year’s ppt decks because they’re not quite in sync. Today’s Class_6 is the end of one last year’s Class_5 plus the beginning of the last year’s Class_6 so it needs a new intro, reminders, learning goals slide.
  • she tweaks the peer instruction questions, perhaps based on feedback we got last time (students didn’t understand the question, no one chose a particular choice so find a better distractor, and so on). The “Astro 101” community is lucky to have a great collection of peer instruction questions at ClassAction. Many of these have options where you can select bigger, longer, faster, cooler to create isomorphic questions. It takes time to review those options and pick ones which best match the concept being covered.
  • like every instructor, she looks ahead to the next couple of classes to see what needs to be emphasized to prepare the students.

“And how,” I asked, “does that compare to last year?”

Between the two of us (I was part of the instructional team, recall) we probably spent 4-5 hours preparing each hour of class. In case you’ve lost the thread, let me repeat that:

Last year: 4-5 hours per hour in class.
This year: 1 hour.

“And do you spend those 3-4 hours working on other parts of the course?”

Nope. Those 3-4 hours per class times 3 classes per week equals about 10 hours a week are now used to do the other parts of being a professor.

Is incorporating peer instruction into classes worth the effort? Yes, absolutely. For both the students and the instructors.

Phases of the Moon

Understanding the phases of the Moon is one of just a handful of concepts that you’ll find in every introductory, general-education “Astro 101” course. “Understanding”, of course, is a terrible description of learning. We have a much more specific learning goal:

After this activity, you [the student] will be able to

  • use the geometry of the Sun, Earth and Moon to illustrate the phases of the Moon and to predict the Moon’s rise and set times
  • illustrate the geometry of the Sun, Earth and Moon during lunar and solar eclipses, and explain why there are not eclipses every month

Everyone who teaches moon phases, from K-16, has their own favourite approach and apparatus. We get 30-40 students for a 50-minute period in our lab, a time meant targeting concepts are better learned in a hands-on environment. Our activity is built around an remarkable, 10-second experience: Students hold a styrofoam ball at arm’s length in a darkened room with one, bright, central light source. They do a pirouette, watching the pattern of light and shadow on the “Moon”.  Ooohs. Aaaahs. Lightbulbs going off. Truly a golden moment.

This page contains materials for what we do for the other 49 minutes and 50 seconds of the lab.


Each group of 3 students gets 2 styrofoam balls, one Earth and one Moon. As the picture shows, we divide the Moon in half and write “NEAR” and “FAR” on the hemispheres. On the Earth ball, we draw the Equator, meridians at 0, 90, 180, 270 degrees longitude (which are 6 hours of daily rotation apart) and dashed meridians on the 45’s (3 hours of rotation apart.) A small sticker represents the observer and the cardinal points help students remember which way to spin the Earth to mimic the daily rotation.

At the center of the lab sits “the Sun”. This is a really bright lightbulb (150 W or more) on an equipment stand. To prevent light from scattering off the floor and ceiling, we built aluminum foil “baffles” that sit above and below the light. They allow only thin disk of light to shine into the room.  The light bulb is set to the students’ shoulder-level so when they hold the Moon at arm’s length, the styrofoam ball naturally goes into the light.


Instructor’s Guide

After running this activity for several terms, we realized there is a lot for the teaching assistants to do and say to keep the activity running. Those instructions eventually found their way into this instructor’s guide.


Unless credit is given explicitly, all documents, graphics and images are licensed under a Creative Commons License Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.  This work is supported by the Carl Wieman Science Education Initiative.

Your feedback, comments, suggestions

If you use the materials here and find a alternate approach, tweak or extension, please share it by leaving a comment.  Thanks!

Why should I use peer instruction in my class?

Image: "Lecture Hall," uniinnsbruck, Flickr (CC)

[Update (June 16): Lead author Zdeslav Hrepic pointed me to a follow-up book chapter [PDF] where he and the study co-authors describe using tablet-PCs to counter the problems uncovered in their study. Thanks, Z.]

I’m sure we’ve all heard it from skeptical instructors: Why should I use peer instruction in my class? In response, we often cite Hake’s 6000-student study or the new UBC study by my colleagues Louis, Ellen and Carl. These are still pretty abstract, though: If you use interactive, learner-centered instruction, you can expect your students to better grasp of the concepts.

“Sure, but why?” the instructors ask. “Why does it work?”

I just read a paper that can help answer that question. I ran across it while following a discussion about the Khan Academy videos and whether or not they are good tools for learning. This paper by Hrepic, Zollman and Rebello (2007) asks students in an introductory physics course and physics experts (with M.Sc’s and Ph.D’s) to watch a 15 minute video of a renowned physics educator presenting a topic in physics.

The researchers do a series of pre- and post-tests and interviews with the students and experts to compare their understanding of the concepts covered (or not) in the video. There were some significant differences. A couple that stick in my head. (1) students recalled learning about concepts that were not presented in the video. (2) Only students who knew the correct answers on the pre-test were able to infer the concepts from the video (that is, the questions were not explicitly answered in the video.) The students who did not know the concept before were unable to make the inferences. Like I said, there are significant differences between what the instructor thinks a lecture covers and what the students think is covered.

The paper nicely gives us some suggestions to counter this problem.

And my thoughts about how to use peer instruction to do that.

Making inferences: Experts make more inferences than students. And only students who already know the concepts can infer them from the lecture. Therefore, instructors need to be cautious about relying on students to fill in the blanks.

Some of the best peer instruction questions are the conceptual questions where the answer is not simple recall. No traxoline here, please. Questions that rely on students making inferences are excellent for promoting discussion because it’s likely students will interpret the question differently, make different assumptions and come to different conclusions. <soapbox> All the more reason that students need to first answer clicker questions on their own so they’re prepared to share their inferences. </soapbox>

Prior knowledge: Students’ prior knowledge influences what they perceive and can “distort” their recollection of what the lecturer says. Therefore, it’s essential that the instructor has some idea of what the students already know (particularly their misconceptions) before presenting new material.

A few, introductory clicker questions will reveal the students’ prior knowledge. Sure, maybe these are simple recall questions that won’t generate a lot of discussion. But the students’ responses will inform the agile instructor who can tailor the instruction.

Continuous feedback about students’ understanding: The trail the instructor blazes through the concepts and the path the students follow often diverge during a lecture. The instructor should be continuously gathering and reacting to feedback from the students about their understanding so the instructor can shepherd the students back on track.

Observant instructors can gather critical feedback from the discussions that occur during peer instruction or the students answers on in-class worksheets like the Lecture-Tutorials popular in introductory “Astro 101” classes and other hybrids of the Washington Tutorials. Rather than waiting weeks until after the midterm or final exam to find out students totally missed Concept X, the instructor can discover it within minutes of introducing the topic. Minutes, not weeks! The agile instructor can immediately revisit the difficult concepts. Immediately, not weeks later or never!

I’m much more confident I can answer the skeptical instructor now. “Why should I use clickers in my classroom?” Because they give the students and you to ability to assess the current level of understanding of the concepts. Current, right now, before it’s too late and the house of cards you’re so carefully building come crashing down.