I was thinking about something only tangentially related to grading, when it struck me that the way we go about generating student grade point averages is the kind of mind-bogglingly stupid system that requires lots of smart people working together to produce. Two very different groups of smart people, with very different ways of looking at the world.
As a scientist, the starting point for assigning grades is generally a set of scores on a bunch of individual assessments. These are generally combined to form some sort of weighted average, which can be expressed as something like a percentage of the total possible points earned. This percentage is then converted to a letter grade (possibly with letter-plus and letter-minus steps, depending on the institution). Then those letter grades are converted back to numbers based on the four-point scale, and those numbers are averaged to produce an overall GPA. Which is reported to three decimal places so we can rank-order students.
But from a signal-processing sort of standpoint, this is remarkably stupid. I have what is basically a continuous analog signal in the initial percentage grade, which is then crudely digitized into a letter grade with a limited set of discrete steps, and then converted back to an analog signal by averaging a bunch of letter grades. The middle step of converting to a discrete letter scale then converting back is pointless at best, and probably introduces extra noise. You’d be much better off averaging together the original percentage scores.
But, of course, I say that because I’m a scientist, and my classes tend to involve lots of grades that are easily rendered into a roughly continuous numerical format. The letter-grade scale is a foolish and clumsy add-on to this. Faculty in “the humanities,” though, and others teaching classes where the vast majority of the final grade is determined from a single paper are much better served by the cruder letter-grade scale– they’re starting with grades that naturally fall into a smaller number of reasonably discrete categories.
But, of course, we have to do something to summarize the performance of students in a compact manner, and employers and graduate schools want rank-ordered lists of class standing, and the false precision of extra decimal places has a seductive allure. so we’re stuck with this foolish system of crude and pointless intermediate discretization…