I posted about this practice sheet last year, but since my photos from last year were all lost when the *Posterous* platform went dark, I figured I’d post about it again!!

I made the worksheet in order to promote a discussion about what type of graphs made sense to create from our data, rather than just declaring which graphs should be made. Each of the graphs shows the same data, displayed differently. On the back of the sheet, students make observations about the graphs, then weigh in on which of the graphs they think is most useful for making predictions.

In ninth grade, students have a variety of opinions on this. Graph A is really attractive, and it’s easy to see how many marbles each bridge supported. Graph C conveniently “has a slope of 1,” as a student said today. Graph D seems to better show the change from one point to another, which would be really important for making predictions if we believed that this wasn’t just due to variability in the phenomenon.

At the beginning of the discussion, we vote on who thinks each graph is most useful for making predictions, then we talk about it. It may take a few rounded but eventually we come around to consensus that best fit lines are very handy when predicting values! Those bar graph lovers can be pretty persistent, though. One student voted for the bar graph twice, but when I asked him how he used the bar graph to make predictions, he said that he’d actually used the best fit line!!

##expdesign ##physicsfirst ##graphing ##practice

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