Posted by Suki Husain on Thu, Feb 25, 2010 @ 11:17 AM
We've all heard the clichés, "Try to turn a negative into a positive," or even "Ignore the negatives in life and focus on the positives."
But what happens when those negatives are numbers?
We're currently in the process of designing a new graphing applet for the National Council for Teachers of Mathematics (NCTM). It will be available on their Illuminations website, along with all the other free math applets that we've developed for them over the past few years.
We were feeling rather happy after sending off the first prototype for review and quite confident that we had designed and anticipated every issue or bug that might come up.
"Au contraire sistaire..." as my best friend's son likes to say.
We got the reviews back this morning and the uber smart math geeks at NCTM had us stumped with this seemingly innocuous comment:
"The pie graph option should have a default for checking whether the series input is valid or not for that representation before attempting to display the graph. By clicking on the pie graph button with negative values in the series, the applet froze."
Hmm...okay. So yes, we could and probably should check if a data series has negative numbers. But then what?
After wracking our brains for a few minutes we decided to check how the world's most famous chart drawing program on earth (a.k.a. Microsoft Excel) handles negative data.
Lo and behold, it doesn't! It basically took all the negative numbers and made them positive, without so much as a friendly warning saying that it was doing that! Could that be right?
We next turned to another great graphing applet from the folks at the National Center for Education Statistics (NCES) http://nces.ed.gov/nceskids/createAgraph/
They chose to simply ignore the negative numbers as if they didn't exist and only display the positive values in the pie chart. Could that be the right option?
Then I asked one of our own teachers, a former Teach for America graduate, and without any sign of hesitation she said "You could simply display a message like: This is not an appropriate representation for this data set."
So here's my question to all you smart math folks out there: Which one of these options would you choose?
Option A: Microsoft Excel way - make the negatives positives
Option B: NCES way - ignore the negatives
Option C: Classroom Teacher - pop up a Data Set Not Valid message
Option D: All of the above + an option to select A, B or C
Option E: None of the above - I have my own solution.
Leave a comment and maybe we'll even graph all the responses -- in a pie chart, of course!