Informing students in the syllabus that the scale represents grade guarantees can also soften criterion grading. Because they assign grades by comparing student scores, curves are easily adaptable if test scores are low. This can lead to cutthroat competition, or even deliberate sabotage. Of course, the curve can be moved up or down at will, so it, too, is subjective. Perhaps the only advantage of curve grading is that one can often reduce student complaints by looking for breakpoints in the scores to use as boundaries.
Professors often use curve grading because test scores are low.
If a test is a disaster, adjust the scores but continue to use criterion grading. Essentially a variation of curve grading with an aura of statistical objectivity, T-scores convert raw scores into a distribution with a mean of 50 and a standard deviation of 10. With the exception of the very top and bottom students, every student in your classes could have his or her grade changed under a different grading scheme. Selecting a scheme is not a trivial matter, and deserves as much care and thought as any other aspect of your teaching. Phillip Wankat is the Clifton L. Lovell Distinguished Professor of Chemical Engineering at Purdue University.