Time for a little math myth-busting. Teachers hate grading as much, if not more, than students hate taking tests. One of the most hackneyed teacher lounge jokes goes something like this:
teacher 1: How’s it going?
teacher 2: Just gave a test.
teacher 1: Grading, ugh!
teacher 2: I’m just going to throw them down the stairs, and see what they get.
…both teachers laugh
The underlying assumption is that throwing something down the stairs gives a nice distribution and saves the teacher the effort of correcting. Is it true that this method tends to produce a normal distribution? For the unfamiliar, this is the picture we are looking for
I threw a set of exams down my basement stairs. I wasn’t really sure how to go about it. Was a slide or toss in order? I did both just to be safe. Here are the results.
As you can see, the results are anything but normal. I wasn’t surprised that it didn’t work. I was surprised at how badly it distributed them. I thought maybe the problem was the carpet. The joke is so old they probably didn’t have carpet when it was first told. So, I threw the tests down my other set of stairs–no carpet.
As you can see, not much better. Maybe it’s my pitching arm?
pic of normal curve from Measuring Usability
Yeah, stairs are lousy. Too notchy.
Make a bullseye and drop them from a height, that should be nice and normal. No wind though.