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The Merits and Demerits of Grading on a Bell Curve

July 15, 2011 13 comments

This entry will touch upon the good, the bad, and the ugly aspects of grading on the infamous ‘Bell Curve‘.  For those of you unfamiliar with either this grading practice, or normal distributions in general, let me briefly elaborate:

Now, for the sake of brevity, I will try to spare you from all of the mathematical gobbledygook and statistical mumbo-jumbo that traditionally comes with these sorts of explanations.

1.  What exactly is a bell curve?

A bell curve, or more specifically, a Gaussian Distribution, is a symmetric curve that is pronounced in the middle, and tapered off at the edges (it really does look like a bell).  As such, the middle portion under the curve contains more area than either of the ends.

 

This is what a typical bell curve looks like.

 

2.  What does “grading on a curve” mean?

When courses are said to be “marked on the curve,” this usually means that a predetermined percentage of students will obtain each grade.  For example, a certain amount of students will receive an A+ (top 4%), a certain amount will receive an A (next 7%), and so on and so forth.  Ultimately, the distribution of grades will fit ‘nicely’ on a bell shaped curve; with the majority of students obtaining marks near the middle portion of the curve (‘B’ range).  Unfortunately, however; this also necessitates the fact that a certain percentage of students will inevitably obtain ‘F’ grades, and fail the course entirely (bottom 6%). Continue Reading >>