July 16th, 2013 by Dan Meyer
Head over to the exercise. Complete a couple. What pedagogical mistake has Khan Academy made in the highlighted lines? How would you fix it?
Don’t get put off by the code. If you’ve taught box-and-whisker plots, you can sort out the issue here.
[via Travis Olson]
Brian lands it:
This code will always generate 15 data points, and these points will not have any outliers (outside 1.5 * (Q3 – Q1)), so students can just pattern match and drag the lines to the 1st, 4th, 8th, 12th, and 15th places once they’ve sorted the data. It’s kind of fun the first time.
Dan Anderson piles on:
Agree with Brian. Always 15 data points? Never have to deal with “having two medians”? Ever? The data is between 0 and 15 (never -40 to -30, never 100 to 1000, never 0.80 to 1.15)? No outliers? Always starting with the data and making a box-and-whisker, never using the box-and-whisker to make conclusions?
Peter Franza picks on a different issue:
I think the largest error is the reliance on random numbers to provide a set of assessments that test an actual set of knowledge.
Random number generators are great for creating a large set of problems that are all basically the same, but in my experience you can provide better assessments/examples with a much smaller set of questions that are designed to illustrate the concept.
Others have danced around it, but the fundamental flaw (as in some, but not all, Khan exercises) is that you get
THE SAME QUESTION
seven straight times, without any change in structure or difficulty, even though the underlying task has a huge variation in structure and difficulty.
Ben Alpert responds from Khan Academy:
I’ve updated the exercise so that it now includes anywhere from 8 to 15 points, so students are forced to deal with two middle numbers, both in finding the median and in finding the quartiles.