There is a whole lot of math behind grading a paper, especially if you want to curve an exam. Dave Richeson talks about how to curve grades, so if you want to hear the math behind each of the 10 methods, follow the link at the bottom of this post.
When I give an exam to a class, I have an intuitive feeling for how the grade distribution should look. I know, roughly, who the A students are, who the F student’s are, and who the average students are. This comes from their homework, their questions in class, our conversations outside of class, and so forth. Individual students may surprise me and do better or worse than I expected, but as a whole, I know the strength of the class when exam-time rolls around. If the class does significantly lower than I think they should have, I will consider curving the exam.
Before you do any curving, you must determine what you want the curve to accomplish. Determining this will help you choose which curving technique to use. Here are some questions to ask yourself:
Do you want a particular average?
Do you want to give the lower-scoring students more of a curve or the same curve as the higher-scoring students? (Rarely do we want weaker students to get less of a curve than the stronger students.)
Do you want everyone to get a passing grade on the exam?
Is it OK to have a big group of A’s?
Is it OK for some students to have a grade over 100%?
Below I present ten techniques for curving an exam score.
1. Return, rewrite, regrade
2. Flat scale
3. High grade to 100%
4. Linear scale
5. Remove a question from the grading
6. Root functions
7. Bell curve
8. Extra credit problems
9. Grading by gravity
10. “I don’t believe in grades”/”I’m a grouch waiting for retirement” grading
If you want to hear what’s behind each of these 10 methods, click here.