<p>Remember a while ago, some of you kind folks were helping me to understand about grading curves? Would you help me understand how that might work based on this hypothetical (obviously this isn’t all inclusive),</p>
<p>imagine for a second that there’s a science class that involves three tests. The hypothetical student scores 83, 78, 74 on them. The class average on the tests were 69, 62, 64. How would a curve work or would that not apply? I guess what I’m saying is that if a student got exam grades that wouuld have stunk in high school, but were at the top of the class in college, would the student (generally, of course) receive the icky score earned or would it be based on his/her relationship to everyone else. I know you can’t speak for a specific teacher, but would anyone be kind enough to give some thoughts on this?</p>
<p>I know in one course I’m taking that the professor adds the test scores, curves the resulting sums, and then assigns letter grades.</p>
<p>A professor could also average the test scores, and curve those numbers, etc. etc.</p>
<p>It becomes trickier if the tests have different weight, or if problem sets, homework, papers, quizzes, etc. play a part. I suspect each professor has their own technique.</p>
<p>I would think that if a professor is curving, it’s because she is aiming for a certain distribution of final grades. If that’s the case, it wouldn’t matter what the individual test curves are, she’d have to recenter everything at the end anyway, so why not just wait until the end? My son says that most of the time, he is unaware of what the final grade is really going to be until the fat lady sings. I don’t think you have too much to worry about if you have been at or above mean for all the assignments/tests.</p>
<p>in order to “curve” a test you would need to know the scores of all the students. Essentially, the top 10% get As, the next 20% get Bs and so on. (The above percentages are only examples.) If the best scores on the three tests happen to be 83, 78, and 74, the hypothetical student gets an A.</p>
<p>All we can say with the current data is the student should get better than the grade assigned to the “average” students (which I would expect to be no worse than a C.)</p>
<p>"
would think that if a professor is curving, it’s because she is aiming for a certain distribution of final grades. If that’s the case, it wouldn’t matter what the individual test curves are, she’d have to recenter everything at the end anyway, so why not just wait until the end? My son says that most of the time, he is unaware of what the final grade is really going to be until the fat lady sings. I don’t think you have too much to worry about if you have been at or above mean for all the assignments/tests."</p>
<p>I’m trying to understand what a curve actually is. I didn’t go to college and see references to it often, so I was hoping someone could help me understand it in some fashion.</p>
<p>Well, you know that the process of curving, right? What the summation thing means is that the teacher adds up the grade on each test, and using those sums to curve. So with 3 tests, the average might be 210 (70 on each test, effectively).</p>
<p><em>edit</em> Didn’t see that you don’t know what a curve is.</p>
<p>Basically a teacher takes grades, and creates a normal distribution (linked to in the above Wiki article) using their average and standard deviation (if you’re not following these terms, look them up on Wiki). Then, students’ scores are assigned grades based on their place relative to the standard deviation of the normal distribution, generally.</p>
<p>As my son explained it to me (explaining what his chemistry teacher told his class), the median score and median grade (2.5) will line up, people with grades at least one standard deviation above the mean will get As and one standard deviation below will get Ds, and Bs and Cs with their attendant plusses and minuses will be distributed accordingly.</p>
<p>This is completely up to the professor. My S recently received the third highest score on a brutally difficult physics midterm, but the prof announced that since all the scores were so low, he was only going to give an A to the single highest scorer. In a different physics class, when the scores on the first midterm were low, the professor apologized for his poor teaching, curved the exam so that scores in the 60s were in the A range, and scheduled an extra midterm to give students an opportunity to bring up their grades. It is completely at a professor’s discretion.</p>
<p>Also, even if a prof curves, it is up to the prof to establish what the median grade will be. Outside of engineering, perhaps, medians rarely seem to be Cs at my S’s college. Most profs these days seem to set the median at B (B- for a “hard” prof, B+ for an “easy” grader.)</p>
<p>I used to be a fan of curving and became less so the older I got. I’ve grown into an either you get it or you don’t as far as A-level work goes and then work downward from there. (Though once I took a test where 19 percent on the curve was an A…too bad I got a 12. It was an engineering course. Shortly thereafter, I was no longer an engineering major.)</p>
<p>Then there’s the old chestnut:</p>
<p>A: leaps tall building in single bound. Faster than a speeding bullet.</p>
<p>B: must take running start to leap tall building. As fast as speeding bullet.</p>
<p>C: can make it over low buildings with effort. Shoots bullets fairly well.</p>
<p>D: takes stairs and elevators. Not too dangerous with water pistol.</p>
<p>F: does not recognize buildings. Wets self with water pistol.</p>
<p>Thank you. You’ve been very helpful. I’m not looking to see her grade, but to understand some of the possibilities when a teacher indicates on his syllabus that he “curves.”</p>
<p>Very simply, a curve allows the students to be graded in relation to each other. Most professors use a bell curve which looks a bit like a hill (or a bell). You mark grades (A, B, C, D, F) along the x axis and number of students along the y axis to get this curve. That means that most students will get an average grade, say it is a C, whilst a few will get Bs and Ds and even fewer will get As and Fs. </p>
<p>In the graph, C will be the highest point, with the most students, and then it will slope down either side from there. In this curve, it doesn’t matter if the average mark scored is 95 or 45, it is average and it is therefore a C. </p>
<p>Once you have set the average point, the C, you then grade the others in relation to that average point. Some people will use standard deviations, other will just decide they want a certain number of As, Bs, Cs, etc to make a perfect bell. That is a standard bell curve. Other professors will curve in different ways to suite their needs or how they perceive the class has done relative to their expectations.</p>
<p>Ah, yes, the good old Gaussian distribution. You can also think of it this way-</p>
<p>Say the prof has 100 students; he wants 20 students to get A’s, 40 students to get B’s, 20 students C’s, and 20 D’s and F’s. All he really has to do is tally the total number of points per student, start at the top and work his way down. In this way, he can set up any kind of distribution he wants. He can pass everyone, or he can flunk half the class. It depends on what he wants the final distribution of A’s through F’s to be.</p>
<p>What really throws a monkey wrench into curving is when the profs allow one dropped test or quiz grade (your lowest). That’s when and why students really don’t know where they stand until the final grade is published.</p>
<p>And what I don’t get about curves is why any professor would want 20% of his class to get Ds and Fs. To me that’s a reflection of being a bad teacher. </p>
<p>I know a lot of science teachers don’t tend to agree with me. My dh’s department expends a great deal of effort making sure their histology exams have grades that fall along a pretty little bell curve. They get all fussed if they make an exam that is “too easy” with grades bunched up in the wrong places.</p>
<p>mathmom,
I was just making that up. But I do know that in some large publics, where thousands of starry eyed kids enter wanting to study medicine or engineering, there is a certain amount of weeding out. It’s not so much that profs are intentionally failing otherwise qualified kids; it’s more that some kids may be going in a direction that they aren’t very well-suited for. They eventually find their niches, though. That’s what the advisors are there for.</p>
<p>ZM: A system that I have often seen, with slight variations, in classes with roughly a Gaussian (normal) distribution of scores:</p>
<p>The class average is said to be a specific grade, let’s say a B-. Anything over X standard deviations above the average (1.5 would be typical) is an A. Anything between Y and Z standard deviations below the average (say, 0.5 and 1.0) is a C. Anything more than N (say, 2.0) standard deviations below average is an F, with grades between Z and N being a D and grades between Y and X being a B.</p>
<p>Non-Gaussian distributions are a little more complicated, but in my experience tend to be curved in a similar way; it just makes for an odd grade distribution.</p>
<p>There’s also the system used in my high school AP French Lit class, where we were graded by “percentage” but the highest grade in the class was considered 100%, regardless of the number, and everyone else’s grade was based on percentage of that score.</p>
<p>The curve may depend on the difficulty of the exam. Say that a prof either inadvertently or deliberately designed an exam that was extra difficult; s/he may grade differently than for an exam that was of a more ordinary difficulty. After sending out grades, a prof had a look at previous exams, and decided that his course had covered more materials than in previous years and upped everyone’s grade. The curve remained. But suppose he found that one or two students had done spectacularly well. They’d get As. The rest would have to be graded up but not as high as those two students.</p>
<p>I think SamK, 1of42, JHS, and others have it nailed BUT there is that not rare enough creature who “curves” but then without much warning decides the top is not “top” enough and gives zero A’s.</p>
<p>" think SamK, 1of42, JHS, and others have it nailed BUT there is that not rare enough creature who “curves” but then without much warning decides the top is not “top” enough and gives zero A’s."</p>
<p>Yeah, I realized even with a curve 20% was probably an exaggeration :), but I’ll never really understand why you can’t weed out kids with Cs or even a conference.</p>