Statistics and Grade Inflation

If sex sells, then grade inflation is the new hookup culture—something that’s a hot topic yet not so much different than it was in the past. With clever phrasing, it makes headlines. The Tuesday announcement that the median grade at Harvard is an A- and the most commonly awarded grade is an A was met with a flurry of support, antagonism, and apathy.

Now, I’m an open critic of grade inflation, but I feel that the recent reports are intuitively deceptive and have elicited a response far beyond the appropriate amount. So I’d like to dispel a few unnecessary reactions that are floating around, and I’d like to do so by running through some statistics.

First, let’s clarify what it means for the most common grade to be an A. It does not mean that most Harvard students mostly receive A’s, that the average grade is an A, or even that the majority of grades are A’s. It means that the most frequent grade, compared to all others, is A. A thought experiment: A class has 100 students, where ten students get A’s, nine get A-minuses, nine get B-pluses, nine get B’s, and so on through D-minuses. Although 90 of the 100 students do not get A’s, the most frequently awarded grade is still an A. The pervasiveness of this mark, which represents 10 percent of the given grades, is much different from the idea that more than 50 percent of grades are A’s.

Now, the distribution of grades at Harvard is not as uniform as in the above example, so we turn to the median to try to make sense of Harvard’s grade distribution. It’s important to stress that saying the median grade at Harvard is an A- (or 3.67 on the GPA scale) is completely different from saying the average grade, and therefore average GPA, is a 3.67.

The median just says that 50 percent of grades are A- or above, and 50 percent are A- or below. In fact, the average GPA is likely lower than 3.67 since the distribution of grades is likely skewed to the left; you can’t go much higher than an A- but you can go much lower. So very poor grades pull the average GPA down more than very high grades pull it up, despite the fact that they affect the median in the same way.

Finally, since A and A- grades must comprise at least 50 percent of grades, and since A is the more common of the two, the smallest possible percentage of A’s must be a little more than 25 percent. (It is worth noting that A-minuses probably comprise the lower half of the distribution too, so the percentage of A’s is likely higher.) Eight years ago, 48.3 percent of grades were in the A range. Only a 1.7 percentage-point increase in the number of A-minuses would be needed to proclaim that the median grade is an A-. And given the leftward skew of grades, the current average GPA may not be too far from its 3.45 value in 2005. People are acting like things have changed drastically when the recent news is inconclusive.

This should offer solace to many students apparently distraught over the recent news. The student with the 3.8 GPA is, in fact, above average, and in the top third of her class if the GPAs are distributed with a 3.6 mean and a standard deviation of 0.5. The student who earns an A on the assignment does not need to lament that it is meaningless. And, more importantly, the students who are frustrated, wondering why everyone else seems to be getting A’s, need not be worried as that is just not the case. I appreciate the conversations and debate that the recent news about grade inflation has generated, but I want these discussions to be aligned with what statistics, not emotional alarm, reveal.

And the statistics don’t reveal much. That a mark indicating, to quote Harvard’s Handbook for Students, “full mastery” with “extraordinary distinction” (an A) is the most common grade at Harvard clearly indicates grade inflation. And that there are more students with full mastery and extraordinary distinction (those receiving A’s, per the Handbook) than there are students with full mastery but not extraordinary distinction (those receiving A-minuses) defies my understanding of what “extraordinary” means. But these notions (even if ridiculous) are largely compatible with what the distribution looked like a few years ago.

Grade inflation is a sensitive issue that’s best addressed when its extent is understood. I urge Harvard to release informative statistics, like the actual distribution of grades and, more importantly, a distributional breakdown by concentration. This way, we’d have a more focused target and not hurt any specific departments in a corrective process.

When we see statistics like those released by Dean Harris, we may think of grade inflation in the student body at large as one plump balloon. But this balloon is really an assortment of different departmental balloons, each with varying amounts of helium. Let’s ground our positions in illuminating statistics rather than speculation and extrapolation. Let’s find out how much helium is in each balloon before we try to pop anything.

Garrett M. Lam, ’16, a Crimson editorial writer, is a neurobiology concentrator in Lowell House.