Buy that special someone an AP Physics prep book, now with 180 five-minute quizzes aligned with the exam: 5 Steps to a 5 AP Physics 1

Visit Burrito Girl's handmade ceramics shop, The Muddy Rabbit: Yarn bowls, tea sets, dinner ware...

## 13 November 2014

### Why I make students graph data as they collect it

When I run a laboratory exercise, students are required to "graph as they go" -- that is, data are not written in a table for processing later, but are plotted directly and immediately on a graph.  The inevitable question, from students and fellow teachers, is why?  I mean, physics data don't go stale.  The graph is gonna look the same if it's plotted tomorrow.  What is the advantage to insisting on a live graph during the laboratory exercise?

The most important advantage has to do with how students understand experiments. A data table just looks like a bunch of random numbers, both to students and to experienced physicists.  It's when the data is put on a graph that patterns can be seen and understood.  By graphing as they go, students develop for themselves an instinct about how much data is "enough," whether the full parameter space is covered, what further data is useful, etc.

Science teachers are always talking about avoiding a cookbook mentality in the laboratory, in which students mindlessly follow directions trying desperately to get the "right" answer.  Well, here's one way to get students to connect intimately with their data -- as they see the graph develop, they think about and process how the data connects with the physical experiment.  They wonder whether the graph will end up straight or curved, they construct hypotheses in their heads which are borne out or not by the graph.

The practical advantage of "graph as you go" is that students don't write down a bunch of numbers and assume they're done.  I get pushback if students have sat at their desks to construct a graph, then are told "ooh, let's get some further data in this region of the graph."  Aww, man, I thought we were finished.  I even put the track away.  Do we really have to get everything out again and do more?  Can we just do ONE more point, or do we have to do a lot?  Grrrr...

If all data is going on the graph right away, I can walk around the room and suggest right away how their data collection process is going.  Everyone expects and welcomes my input as part and parcel of the lab course.  Lab becomes about producing beautiful graphs, not about getting done and away from the annoying physics teacher.