Test design and grade inflation

I gave an exam yesterday. While I was standing in the copy room making copies, one of the grad students walked by.

“Midterms?”, he said.
“Yes,” I said.
“Grading’s not fun.”
“I hope this one won’t be too bad. Lots of questions with simple answers.”
“Yeah, you think that now, but it’s amazing what they come up with.”
“Sure. My trick is this. I used to write exams to be out of a hundred, and you’d end up with things worth six, eight, ten points and you sweat over partial credit. What’s the difference between a four and a five out of six? Now I write with questions being out of two or three, and I spend a lot less time thinking about that. If it’s out of two, zero is wrong, one is sort of right, two is entirely right or almost so. The grades come out just as accurate.”

The exam in question was out of thirty-six points, with three one-point items, nine two-pointers, and five three-pointers.

I’ve given this spiel before, ever since I discovered this trick. What I hadn’t realized is that it’s a smaller-scale version of Jordan Ellenberg’s take on grade inflation. Ellenberg argues that, first, if GPAs are to be used in order to discriminate between stronger and less strong students, what matters is not how high the grades are but how many different grades there are, so having a scale where the only grades used are A, A-, B+, B, B- is just as good as having a scale where the only grades used are A, B, C, D, F. And he gives the results of some calculations showing that if there are only three posssible grades — or even two, in some dystopian world where the only possible grades are A and A- — we still have some reasonable ability to discriminate between students over the course of an undergraduate career.

(Disclaimer: I’ve met Jordan. He’s also the cousin of a friend of mine I met through different channels. It’s a small world after all.)

7 thoughts on “Test design and grade inflation

  1. This is great! I’m going to follow my own advice, now that you’ve explained to me what my advice is, and do this on the next exam I give.

    1. Meanwhile I’d found your advice about grade inflation interesting for years, and hit on this exam-construction strategy independently after, in my first year at Berkeley, giving a dozen or so 100-point, hour-long exams where I spent too much time debating partial credit.

  2. At my home university in Lund, Sweden, we generally have two or three grades only: Pass and Fail, or sometimes “Pass with distiction”, Pass, and Fail. Easy, clean, unambiguous. The only time the “distiction” bit would ever matter was for getting admitted to graduate school and even there it was far more important what you did for an undergraduate project and where it was published.

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