## Day 31

##### Activity:

Best class period of the year so far! Today went so well.  Students were very engaged and worked hard. From start to finish they were excited about the bungee jump.  We heard students talking about how much they had been looking forward to this and heard them cheer for their groups after an especially epic bungee jump. Today was one of those days where you just absolutely love your job.  Now all that being said, today did not just happen by chance.  We’ve been prepping for it for a while with our lessons but also preparing the students for how to work well in a group and to be independent learners.

As you may recall, the beginning of the chapter we spent the first day collecting data for our Barbie Bungee activity.  We have been using this context throughout the chapter but students haven’t been using their own data until now.  We created a review by going through the text and selecting each learning target that could be used with the Barbie data.  Then we made a review guide that asked questions about each target using the Barbie data, covering everything from making a scatterplot to exponential regressions.  Students worked through the review using an iPad.  They answered lots of questions that were great practice for the test but the main goal was to find the best regression model for their data.

Each group calculated a linear, quadratic and exponential model for the data.  They looked at the residual plots and r^2 values to decide which was best.  Some magic happened here when some groups had a linear and quadratic regression that had similar residual plots and the same r values.  One group compared the residuals that they had calculated in earlier questions to see which was smaller.  Another group elected to go with the regression model with the smaller standard deviation of the residuals. And another group chose linear because they noticed their quadratic eventually started going back down so this was bad because it was extrapolation.  Needless to say, we were very proud teachers.

After each group chose their regression model they began calculating how many rubber bands they would need for the jump of 17 ft (518 cm).  We took Barbie down to the staircase and let her fly! Check out the pictures to see how they did! Spoiler: Some Barbies didn’t make it out alive!

##### Notes

Groups that chose linear models did the best.  The since the quadratic regressions will start going back down after the vertex, the extrapolation was much more problematic than it was for the other models.  Groups that chose quadratic or exponential models tended to be quite short on their jumps.

To best measure how close Barbie gets to the floor, have students stand below the drop site holding meter sticks.  Then use the slow motion video option on an iPhone to take videos.  You can pause or screen shot the results to show students.