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How Do Curves Usually Work?

MDreamsMDreams Registered User Posts: 55 Junior Member
edited December 2012 in Northwestern University
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?
Post edited by MDreams on

Replies to: How Do Curves Usually Work?

  • Sam LeeSam Lee Registered User Posts: 9,449 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.
  • BurdenedBurdened Registered User Posts: 259 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.
  • Sam LeeSam Lee Registered User Posts: 9,449 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.
  • bud123bud123 Registered User Posts: 704 Member
    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?
  • arbiter213arbiter213 Registered User Posts: 3,572 Senior Member
    ^Because the tests are testing objective knowledge.
  • Sam LeeSam Lee Registered User Posts: 9,449 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.
  • LoremIpsumLoremIpsum Registered User Posts: 3,501 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?
  • bud123bud123 Registered User Posts: 704 Member
    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.
  • MDreamsMDreams Registered User Posts: 55 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
  • Crimsonstained7Crimsonstained7 Registered User Posts: 1,300 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.
  • NorthwesternDadNorthwesternDad Registered User Posts: 555 Member
    As long as your science GPA is 3.5 and higher, you will be in pretty good shape for admission to medical schools.
  • PieceofToastPieceofToast Registered User Posts: 253 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.
  • Crimsonstained7Crimsonstained7 Registered User Posts: 1,300 Senior Member
    Yah, my brother jumped too high after placing out of a math, and so he ended up doing terribly. I think it's wise to consider not skipping into harder subjects.
  • PieceofToastPieceofToast Registered User Posts: 253 Junior Member
    Addendum to my earlier post:

    Got a tentative grade from my prof. Said that (approximately; they eyeball the distribution) the top 35% get A's, and the next 35% get B's, and the distribution goes from there.
This discussion has been closed.