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# How Do Curves Usually Work?

edited December 2012
I'm interested what the average in a class gets curved up to.

For example, after two tests in a certain class, the average is a 65.75. What does this become? And does that percentage become a C+, B-, B? And what percentage above the average do you need to have an A?
edited December 2012
14 replies
Post edited by MDreams on

## Replies to: How Do Curves Usually Work?

• 9273 replies176 threads Senior Member
it's really up to the professors.

1.x% = A, y% = B, etc.
2. average = B, 1 std deviation above the mean = A, etc.
3. combo of 1 and 2
4. other methods.

In general, intro sci/engg classes have the toughest curves. I am not really sure why. Maybe since these classes have bunch of premeds, some profs think they are doing the society a good thing by weeding out people who shouldn't be doctors. But a B or C at NU could be a A in plenty of other places. So it kinda blows.
• 258 replies1 threads Junior Member
Still HS, but of the teachers I've seen, most of them are doing the normal bell curve.
Things like 85%- A; 70% - B; etc are technically scales, not curves.
• 9273 replies176 threads Senior Member
^The x and y in my previous post represent the population, not the scores. It's not your fault; I just wasn't clear. The professor decides the percentage of people that would receive a certain grade. The curve doesn't even need to be normally distributed. The curves at NU often don't resemble anything like a normal bell, which fits more nicely in HS where the caliber of students is usually of much wider range.
A bell curve works with a typical mix of students but is silly at a place like NU. All the students are in the top 1% of test takers in the world, 2.5 SD above the mean. If you use a bell curve, with the subset of students at NU, the students on the left side of the bell curve are still 2.5 SD above the best students at other universities but end up with a C or D.
And why do faculty feel they need to have a test average score of 68% when the students in the class are the best and brightest students in the world?
• 3501 replies71 threads Senior Member
^Because the tests are testing objective knowledge.
• 9273 replies176 threads Senior Member
^^Because it allows the professors to differentiate and assign grades accordingly, especially when the profs don't want to give too many A (e.g. premed science courses). I remember my organic chemistry courses had that kind of average and the professor would say something like "you guys did a great job". Our chemistry department is one of the top in the world and top-5 in the US according to NRC; that's a compliment from one of the leading experts despite the seemingly low averages.
• 3481 replies20 threads Senior Member
And why do faculty feel they need to have a test average score of 68% when the students in the class are the best and brightest students in the world?

It could teach a little humility to students who have spent years in K-12 taking watered down tests that never challenged them. After such a wake up call, some students double down their efforts; other decide that maybe that major isn't really for them: isn't it better they find out now rather than in junior year?
It's sad to see a bright kid at NU end up on the left side of the NU curve and make a C or D and give up their dream to be a physician. If the same student went to most any other school he would have been at the top of the class setting the curve and well on his way to his dream career as a physician.
My point is when you start off with students in the top 1% in the country the bell curve doesn't apply. One would expect a majority of the students in this "subset" of students to earn an A's in most of their classes.
• 40 replies15 threads Junior Member
Yeah I'm pre-med. And I've wanted to be a doctor for a long time. I really don't want that to happen to me... haha
• 1282 replies18 threads Senior Member
By bending from their straight position. Oh, that's a knee slapper. See, he asked "How do curves usually work?" and I said they bend. Oh, I slay myself ;-)

In all seriousness though, a few C's or D's on tests at NU isn't going to mean much, especially since an NU degree will already be one of the top degrees anywhere.
As long as your science GPA is 3.5 and higher, you will be in pretty good shape for admission to medical schools.
• 251 replies2 threads Junior Member
My math prof explained that they guarantee an A to, say, scores 90% and above, B to 80%, and so on. Then they have a benchmark for about how many students they want to get an A, a B, etc., then they eyeball it. So there isn't a concrete curve that the department uses to calculate everything precisely, but they do have a certain distribution that they're aiming for. He's also insinuated that the curve is weighted a bit to give more students slightly higher grades than a more strict curve might do.

Random aside: If you're offered placement into an advanced course (Math 230, Chem 171--the various advanced sequences/placements), be open to the possibility of dropping into a lower class during add/drop. "Maybe it'll get better" isn't a thing, but curve-wreckers definitely are.