Friday, November 9, 2012

The perfect grading strategy, or: How to benefit from your own research

Grading exams is one of the burdens of being a teacher, especially when it is a large course. My biggest course has approximately 120 students, which means that right now 120 exams consisting of 6 essay questions each are sitting on my desk.
What is the right grading strategy? There seem to be two strategies.
One is to do one exam at a time, and grade all six questions. There are several problems with this approach. The main problems is the risk that your standards start drifting: if students are bad on average you may become more forgiving, or more stringent if they do well. The second problem is the change of mindset necessary after each question, which is mentally taxing and time-consuming.
The second strategy is the one I think most people use, which is to grade all question 1's, then shuffle the whole stack of exams, grade all question 2's, etc. This seems to be the perfect solution that solves the problems of strategy 1: your standards are less likely to drift, and if they do the effect is more randomly distributed. You also don't have to shift mindsets, because you grade the same question over and over again.
So isn't strategy 2 the perfect method? Unfortunately not. When reading and grading answers that are all similar but not the same it becomes increasingly difficult to separate them in your mind. Each new version of the answer needs more mental focus to keep it apart from the previous answers from other exams. That is why I often use this as an example of a case where interruption is beneficial instead of harmful: an interruption helps clearing the mind of previous answers, reducing interference. But regular interruptions do not, of course, speed up the process of grading, and as we all know interruptions often lead to more distraction.
The solution is so simple that I wonder why I haven't thought of it before. Isn't it obvious: grade TWO questions per exam, so first all questions 1 and 2, then all question 3 and 4, etc. Alternating two questions delivers just the amount of memory interference needed to disentangle the current answer from previous answers. Keeping two answer standards in mind is still doable, and the standard drift is also reasonably under control.
I am now halfway through with grading, and although there still a lot of work to do, I can report that it works very well, and I can recommend it to everyone in the same situation.


  1. So now, to test your new strategy, you will divide the rest of the exams between several other people, who can then test this strategy by grading the other exams and reporting their findings back to you?

    That seems like a valid scientific approach.

  2. Trudy, do I understand that you volunteer to help grading my exams?

  3. I think your blog entry was half way through the process. What did you think after completing it?

  4. Hi Bill,
    Halfway through was already enough for me to decide that I liked it, and that didn't change after I was done. I am currently working through another stack, and using the same method.