Wednesday, May 26, 2010
Granularity of Grading Scales
One thing that has always bothered me is the granularity of grading scales. The point of the exercise of giving a grade should be an attempt to classify how well the student learned the material. It seems reasonable to classify this level of understanding into “not at all”, “not very much”, “ok”, “pretty well”, and “excellent”, which seem to correspond to the typical F,D,C,B,A. What does NOT make sense is to assign a number on a scale of 0-100. A grade of 67 seems to indicate somehow that 67 percent of the material was learned. This is, however, not at all the case. Rather, it means that the student answered 67% of the particular questions posed on this assignment correctly. It is extremely rare for faculty to ask exactly the right set of questions to determine if every concept was learned in a reasonable way, so this number seems just about meaningless. I have always been in favor of oral exams. I find it extremely easy to, within a 5 minute conversation with a student, classify their understanding of what they should have learned into one of the five categories described above. I guess at some level you’d have to buy into my “Teach the Why not the How” concept (http://daviddoria.blogspot.com/2010/05/teach-why-not-how.html) to realize that it doesn’t really matter if a student is able to produce the correct numerical value on an exam question, but it is EXTREMELY CRUCIAL that they understand the general “what is going on”. I understand that in large classes they are not reasonable, and this would certainly need to be addressed in order to implement such a system on a large scale.