| Curving means using the average and standard deviation from a class's scores to assign letter grades. Here it is usually done to a C+/B- curve, which is lower than the B+/B curves I have heard about from friends who go to HYS. In a normal distribution, ~68.2% of the population lies within one standard deviation from the mean. If the mean is set to the C+/B- boundary, this means that roughly 68% of the class gets between a C- and a B+. If the curve is symmetric (as it should be if parametric stats are applied, though I don't think a lot of professors actually care about the assumptions because a lot of the distributions at Duke end up being bimodal), then this means that only ~16% of the class will get A-level grades, and ~16% will get D/F's. Considering the uproar when Princeton cut back its portion of A's to 35%, you can understand why Dukies sometimes complain about grade "deflation" here.
A-/A/A+: 13.6+2.1+0.1 = 15.8%
B-/B/B+: 34.1%
C-/C/C+: 34.1%
D-/D/D+: 13.6%
F: 2.1+0.1 = 2.2% |