Final time came and went and I managed to get 100 on my AP European History final and more than a hundred on my Chemistry final. I managed these feats because they were curved. To prevent possible misunderstandings I will describe what my teachers did to curve it, in case it is unusual or something. They took the number correct out of a number slightly less than the total. For example there were 80 points on the History final. I missed five and hence got a 75/80. But there was a curve so it was 75/75.
Why is it called a curve? It doesn’t seem curved. When graphed it is a straight line.
I understand the mechanics of “the grade curve;” but I’ve never been curved in any of my classes. What I don’t understand is the theory of the grade curve. What is the theory behind the curve? Why would a teacher/professor give something for nothing? The fundamental principle of taking a class is to learn something, not to get a good grade. What gives?
The idea behind proper curving is that the best performers in the class get the best possible grade and the worst performers get the worst grade. That idea is rarely honored, rather everybody gets a small bump up by recentering the grade.
The original idea is that there are no objective grading standards and if you use one-size-fits-all scale then people who are at the top and learned the most they could still get less than perfect grades.
I think it’s called a curve because to be fair, the test scores should follow a normal distribution or bell curve. This way, a few people do really well, a few fail, but most do average (the mean score). If the distribution of scores is skewed, then the Prof. may want to change some things around so the scores are normal.
Of course, just giving a few free points to everyone may not make it normal, but will make it a little better.
Yes, a curve is set to artificially fit an actual set of scores into a bell curve. When there is a curve, it means that grading amongst you and your classmates is a zero-sum game, i.e. you are not being judged on what you know as much as you are being judged on how well you fare against your fellows.
The curve is good for averaging out teacher skills and preventing grade inflation.
But it’s bad when comparing class to class because if you happen to be in the smartest class ever, you could do fantastic work but still get a bad grade because you happen to be in an especially good group.
From experience, “grading on a curve” can mean a lot of things. What Strinka described is certainly one way. The idea is that you want to “normalize” the test results so that the best scores are adjusted closer to 100% and the average scores are closer to 70% or whatever is deemed an average performance. It is rare indeed to get test results that fit a bell-shaped curve without such adjustments. While I do grade on a curve, I don’t restate scores. I just tell students that if you’re near the top scores, that’s good for a top grade; if you’re near the bottom scores, that’s a bad sign in terms of a passing grade. If you’re near the masses in the middle, that’s safe in terms of a passing grade, but not a top grade.
Splanky has it right, but there’s also the idea that the teacher, going in, wants a certain mean and standard deviation for that bell curve. So if you don’t actually get that mean and standard deviation, you adjust the scores in some way such that you do.
Of course, this is flawed in several ways. Most teachers who “curve” grades don’t really understand the statistics behind it; they’re just giving out some number of points that seems about right to them. And they seldom will decrease scores at all. But even given all that, a bell curve is often not an appropriate choice for a grade distribution. In many classes I’ve seen, the distribution is bimodal, with one clump of people who studied and did the homework, and did well, and another clump who slacked off, and did poorly. While you could transform that in such a way as to get a bell curve, it’s probably not fair to do so, since that would put the worst of the good group (who did almost as well as the best) only slightly above the best of the bad group.
Most of the professors I ever had used one method or another of applying a ‘curve’. The most popular method seemed to simply creating a histogram of the grades. This histogram usually looks like a normal distibution (see earlier post). The prof then picks a spot on the curve to separate the 'A’s from the 'B’s, the 'B’s from the 'C’s, etc.
The “Swarthmore Chemistry Prof Curve Method” seemed to be, “I [the prof] look at all the averages at the end of the semester, then dole out grades as I see fit.” People still called this “curving”. They would often speak of “curving up” and “curving down” (where your actual grade was lower than it would be on a traditional 10-point/letter scale.) I do not pretend to understand all of this.
Thanks for the answers.
I don’t think my teachers were concerned with making normal distribution. They’re high school teachers. I wouldn’t be surprised if my math teacher did that, but my history teacher. Also my history teacher said she reduced the curve because it was evident from our answers that we talked to a previous class about it.
This “curve” is a rather awful misnomer. Proper “curved” grading is a method for applying a letter grade to a numerical one, and doesn’t alter the numerical scores at all. The idea is that a C sits across the median score evenly, and Bs, Cs, and Ds are the same width (in multiples of the standard deviation).
In my department that’s regarded as a sign of bad test-writing. Out of dozens of tests I’ve given and helped score, only a handful had a distinctly non-Gaussian distribution, and all but one of those was basically that the test was far too easy or difficult, so the curve got shoved off one end of the scale or the other.
One of my professors writes tests difficult and varied enough to use the whole range of scores from 0-100, with the mean and median scores being around 45-55%. He then used the class average as a dividing line between C and B; if you either got a straight score of over 85% or were in the top 20% of the class you got an A. He also puts some questions onto the test that weed out those who clearly didn’t have a clue; those are the Fs. I don’t think he gives Ds on exams.
I think this is the best grading system I’ve seen. First, a silly screw-up* that costs you 15 points on an otherwise perfect paper shouldn’t cost you an A - it doesn’t here. Second, it allows the professor to give a test that really tests what you know; if there’s a 30-point question that belongs in a graduate class and very few get the right answer, it allows the professor to reward those who did it without heavily penalizing those who had a good undergraduate-level understanding of the material and no more.
*The classic example of this is when Jason Fox spills root beer on Peter’s calculator and Peter gets unreasonable values for the answers on a physics test.
Curving also happens in some law schools, although in a different way. At my school, for large lecture classes professors got a sort of grading budget. IIRC, they could award no more than 4% A, 8% A-, 20% B+, and 10% C+ or below. Everyone else got a B. In my experience, it fairly accurately representated reality at a competitive law school: most people can do the work (and are inclined to do it), very few people are superstars, and a somewhat larger group are fuckups or have Intefering Life Events.
What does the distribution of raw scores look like? Roughly Gaussian? I’m not saying anything about where the curve lies, but that a well-written test has scores that “look Gaussian”.
This goes back to the “too easy” error. A common problem with test writing is having what we call bad separation. Remember that a true Gaussian curve is characterized by the mean and the standard deviation. Low standard deviations clump all the grades together so it’s tough to tell the difference between two students’ scores. A related problem is where the curve looks Gaussian on the left, but falls off a cliff or runs into the top of the scale on the right. It’s easy to tell the Cs, Ds, and Fs, but it’s tough to tell the As from the Bs. The solution is to add hard questions that you only expect the students who really understand the material to get. This shoves everyone down the scale except those who get it right and restores the Gaussian shape.
I’ve never had a single teacher curve “down” - giving everyone a lower letter grade for a higher percentage grade - only curve “up.” I’ve also never had a teacher look at the total distribution, only the fact that no one (or sometimes only one person) got everything right. The rationale I hear is that either the test or the teaching was flawed (otherwise more people would have gotten perfect scores) and that it’s “unfair” to punish the students for a flawed test or teacher.
:dubious:
I always found the whole thing intellectualy dubious. If we assume the “bell curve” is an ideal representation, then in a class of 30, no more than 2 students should get a A, right? No less than 2 students should get an F. Most of the students should be getting C’s. If your test doesn’t reflect this naturally then either: 1. your test is poorly designed (too easy or too hard) or 2. your teaching is poor (topics aren’t challenging enough or explanations aren’t thorough enough) or 3. The bell curve isn’t, after all, ideal* or 4. your students are codfish. None of these problems is “fixed” by artificially inflating grades.
Then again, most of my schooling occured in the “everyone should get an A if they try really hard” and “B is average” phase of education. Malarcky. When did “self-esteem” become more important than actually learning stuff?
*Which may indeed be the case, and more so the higher the education, as the sample becomes more and more biased in favor of the truly talented. At that point, it seems that following a bell curve means that the really bright are artificially failed even if they grasp the material, while the really, really bright fight it out for the 2 A’s.
Which is why the proper curving method is to take the raw scores, find the best Gaussian fit (a well-written test should have a fairly decent one), and use that mean and standard deviation to assign letter grades. The idea that “90% is an A” is just ludicrous.
Oh, about the late '70s to the early '80s as I mark it.
I have had little experience with “curving” and none of it was good. I can recall several classes in college as well as one in high school where the instructor decided that the overall class score was too low and disregarded certain stumbing questions from the tests. The problem was that I would get those questions right and no longer received credit for them. The way I understand it, this isn’t really grading on a curve but that’s what the school called it :mad:
You are exactly correct: that is not curved grading at all, but a badly-written test and (if this was widespread enough for the school to call it something) abysmal pedagogical standards. What school was this (the college)?