Grade Bias
02 Apr 2016A while back, a study on grade bias based on student attractiveness made the rounds. See here (“For female students, an increase of one standard deviation in attractiveness was associated with a 0.024 increase in grade (on a 4.0 scale)”) and here (“But women in the “less attractive” group showed a much larger gap, earning on average 0.067 grade points less than other students. “)
When I read that, I couldn’t help but think that those are awfully small changes, basically, the difference between a 3.0 and a 2.933 GPA. How could such a small bias play out in reality? let’s assume we have two students who are identical solid “B” students in their academic performance, but one is much more attractive than the other. Let’s see how a bias against one student could look.
##Scenario 1## Everyone is a little biased, and sometimes that is enough to randomly round down a grade. That would result in report cards looking like:
| Hot student | Not Hot | |
|---|---|---|
| Prof 1 | B | B |
| Prof 2 | B | B- |
| Prof 3 | B | B |
| Prof 4 | B | B |
| Prof 5 | B | B |
| Prof 6 | B | B- |
| Prof 7 | B | B |
| Prof 8 | B | B |
| Prof 9 | B | B |
| Prof 10 | B | B |
| Prof 11 | B | B |
| Prof 12 | B | B- |
| GPA | 3.0 | 2.92 |
In this case, three different proffs rounded the unattractive student down a little bit.
##Scenario 2## A few teachers are a little biased and consistently round unattractive students down a little bit. Report card would look like:
| Hot student | Not Hot | |
|---|---|---|
| Prof 1 | B | B |
| Prof 2 | B | B- |
| Prof 3 | B | B |
| Prof 4 | B | B |
| Prof 1 | B | B |
| Prof 2 | B | B- |
| Prof 3 | B | B |
| Prof 4 | B | B |
| Prof 1 | B | B |
| Prof 2 | B | B- |
| Prof 3 | B | B |
| Prof 4 | B | B |
| GPA | 3.0 | 2.93 |
In this case, Prof 2 consistently gave a slightly lower grade to the not hot student.
##Scenario 3## A very small minority of teachers are very biased against unattractive students. Report cards would look like:
| Hot student | Not Hot | |
|---|---|---|
| Prof 1 | B | B |
| Prof 2 | B | B |
| Prof 3 | B | B |
| Prof 4 | B | B |
| Prof 5 | B | B |
| Prof 6 | B | B |
| Prof 7 | B | C |
| Prof 8 | B | B |
| Prof 9 | B | B |
| Prof 10 | B | B |
| Prof 11 | B | B |
| Prof 12 | B | B |
| GPA | 3.0 | 2.92 |
Here, Prof 7 is a real jerk who lowers the not hot student by a full grade.
##Summary##
To summarize the possibilities:
- 100% of people are a tiny bit biased, and it effects the grades they give 25% of the time
- 25% of people are consistently biased (a little bit)
- 8% of people are very biased
or of course
- some linear combination of the above (say, 4% of people are very biased and 12% of people are a little biased)
I think the big takeaway here is that, when it comes to giving out grades, it looks like the vast majority of teachers are fair most of the time. Even if you are attractive enough to be a model, you’re unlikely to get a grade rounded up.
Even with that, no reason to assume you have no biases, so why not grade “blind” (i.e., don’t look at the name on the paper before you grade it)? Costs virtually nothing, and could increase fairness of the course.
**Confession: I did not go and read the paper these articles were based on like I should have. I probably just rediscovered things the authors already knew.