Comments on: How to curve an exam and assign grades http://divisbyzero.com/2008/12/22/how-to-curve-an-exam-and-assign-grades/ A blog about math, puzzles, teaching, and academic technology Wed, 17 Mar 2010 18:27:05 +0000 http://wordpress.com/ hourly 1 By: Sergio http://divisbyzero.com/2008/12/22/how-to-curve-an-exam-and-assign-grades/#comment-1161 Sergio Wed, 17 Mar 2010 18:27:05 +0000 http://divisbyzero.wordpress.com/?p=350#comment-1161 "If there are mostly failing grades then obviously something is wrong with the exam" This is not at all the case. Sometimes a subject is inherently difficult, and yes, failures should be anticipated. Your attitude is what has caused rampant grade inflation - and the eventual decline of America - in the first place. “If there are mostly failing grades then obviously something is wrong with the exam”

This is not at all the case. Sometimes a subject is inherently difficult, and yes, failures should be anticipated. Your attitude is what has caused rampant grade inflation – and the eventual decline of America – in the first place.

]]> By: melissa http://divisbyzero.com/2008/12/22/how-to-curve-an-exam-and-assign-grades/#comment-1100 melissa Sun, 28 Feb 2010 05:30:17 +0000 http://divisbyzero.wordpress.com/?p=350#comment-1100 that is not always true. the professor can word the questions ambiguously and make it difficult for students. If there are mostly failing grades then obviously something is wrong with the exam that is not always true. the professor can word the questions ambiguously and make it difficult for students. If there are mostly failing grades then obviously something is wrong with the exam

]]> By: Robert http://divisbyzero.com/2008/12/22/how-to-curve-an-exam-and-assign-grades/#comment-1070 Robert Thu, 18 Feb 2010 23:28:00 +0000 http://divisbyzero.wordpress.com/?p=350#comment-1070 Thanks for this. I have been using the flat scale, and just accepting there will sometimes be a score or two over 100. I do like the linear scale idea. However, I don't fully understand the justification of boosting the lower scores more. It seems like it is rewarding students who may not have prepared enough. One thought -- could this linear scale formula use medians instead of means? Medians tend to be more stable. Thanks for this. I have been using the flat scale, and just accepting there will sometimes be a score or two over 100. I do like the linear scale idea. However, I don’t fully understand the justification of boosting the lower scores more. It seems like it is rewarding students who may not have prepared enough.
One thought — could this linear scale formula use medians instead of means? Medians tend to be more stable.

]]> By: Liz http://divisbyzero.com/2008/12/22/how-to-curve-an-exam-and-assign-grades/#comment-1025 Liz Tue, 02 Feb 2010 18:47:45 +0000 http://divisbyzero.wordpress.com/?p=350#comment-1025 Math Prof here: Nice website, I am looking for guidelines for inexperienced adjuncts and may use some of your suggestions. Personally, I DO use the bell curve if I have to curve, e.g. when the average is below a 75%. Generally some curve is necessary in calculus I, II. However, I use the curve as a starting point, then do some tweaking. I also am more generous, making the median (not the average!) the lowest B-. That way (before tweaking) half of all students get a B- or above, and half a C+ or below. Math Prof here: Nice website, I am looking for guidelines for inexperienced adjuncts and may use some of your suggestions.
Personally, I DO use the bell curve if I have to curve, e.g. when the average is below a 75%. Generally some curve is necessary in calculus I, II. However, I use the curve as a starting point, then do some tweaking. I also am more generous, making the median (not the average!) the lowest B-. That way (before tweaking) half of all students get a B- or above, and half a C+ or below.

]]> By: Katrina http://divisbyzero.com/2008/12/22/how-to-curve-an-exam-and-assign-grades/#comment-1010 Katrina Fri, 22 Jan 2010 12:03:00 +0000 http://divisbyzero.wordpress.com/?p=350#comment-1010 Thank you! This whole page was extremely helpful with the debacle that was the first exam this term. As a history professor, my first thought was that the gravity method might work for me, but being a secret math geek I really enjoyed working out the linear curve for this exam. I've only used a version of the "flat scale" method before. Thanks again! Thank you! This whole page was extremely helpful with the debacle that was the first exam this term. As a history professor, my first thought was that the gravity method might work for me, but being a secret math geek I really enjoyed working out the linear curve for this exam. I’ve only used a version of the “flat scale” method before.

Thanks again!

]]> By: Emily http://divisbyzero.com/2008/12/22/how-to-curve-an-exam-and-assign-grades/#comment-998 Emily Sun, 10 Jan 2010 21:31:51 +0000 http://divisbyzero.wordpress.com/?p=350#comment-998 Yes, I see what you mean... thanks for the explanation, and for your very detailed post on the subject-- it's brilliant, and has solved my grading dilemma. Yes, I see what you mean… thanks for the explanation, and for your very detailed post on the subject– it’s brilliant, and has solved my grading dilemma.

]]> By: Dave Richeson http://divisbyzero.com/2008/12/22/how-to-curve-an-exam-and-assign-grades/#comment-996 Dave Richeson Sun, 10 Jan 2010 03:40:47 +0000 http://divisbyzero.wordpress.com/?p=350#comment-996 Emily (and Megan), Thank you for making more clear the problem that you have! You are right that I used different variables in the abstract form that I gave above and the example that I gave below. However, BOTH are correct. I'm using the point-slope version of a line. It requires a slope (which I gave in both cases as (y1-y0)/(x1-x0)) and a point on the line. In the first case I used the point (x0,y0) and in the second case I used (x1,y1). They should both give exactly the same function (try both and simplify to see that!). But now I see why it is confusing. I think I'll change the example—to prevent others from being confused about this change in notation. Thanks! Emily (and Megan),
Thank you for making more clear the problem that you have! You are right that I used different variables in the abstract form that I gave above and the example that I gave below. However, BOTH are correct. I’m using the point-slope version of a line. It requires a slope (which I gave in both cases as (y1-y0)/(x1-x0)) and a point on the line. In the first case I used the point (x0,y0) and in the second case I used (x1,y1). They should both give exactly the same function (try both and simplify to see that!). But now I see why it is confusing.
I think I’ll change the example—to prevent others from being confused about this change in notation.

Thanks!

]]> By: Emily http://divisbyzero.com/2008/12/22/how-to-curve-an-exam-and-assign-grades/#comment-994 Emily Sat, 09 Jan 2010 18:53:49 +0000 http://divisbyzero.wordpress.com/?p=350#comment-994 Hi Dave, I'm with Megan above-- isn't there a problem with the formula you provide for the linear curve? (I'm trying to figure out how to apply it myself.) You originally give the formula as: f(x) = y0 + [(y1-y0)/(x1-x0)]*(x-x0) However when you apply it in both examples, you seem to be using the formula: f(x) = y1 + [(y1-y0)/(x1-x0)]*(x-x1) can you check your formula vs. application again? thanks! Emily Hi Dave, I’m with Megan above– isn’t there a problem with the formula you provide for the linear curve? (I’m trying to figure out how to apply it myself.)

You originally give the formula as:
f(x) = y0 + [(y1-y0)/(x1-x0)]*(x-x0)

However when you apply it in both examples, you seem to be using the formula:
f(x) = y1 + [(y1-y0)/(x1-x0)]*(x-x1)

can you check your formula vs. application again?

thanks!
Emily

]]> By: Dave Richeson http://divisbyzero.com/2008/12/22/how-to-curve-an-exam-and-assign-grades/#comment-926 Dave Richeson Fri, 18 Dec 2009 04:58:58 +0000 http://divisbyzero.wordpress.com/?p=350#comment-926 I'm glad it helped. This was a fun post to write. I'm have two stacks of exams to grade right now with a third coming tomorrow. I'm hoping I don't have to employ any curving on mine, but we'll see! I’m glad it helped. This was a fun post to write. I’m have two stacks of exams to grade right now with a third coming tomorrow. I’m hoping I don’t have to employ any curving on mine, but we’ll see!

]]> By: Lori Mathhead http://divisbyzero.com/2008/12/22/how-to-curve-an-exam-and-assign-grades/#comment-925 Lori Mathhead Fri, 18 Dec 2009 04:52:17 +0000 http://divisbyzero.wordpress.com/?p=350#comment-925 Dave, I don't grade papers for a living but I do help my husband keep up with grading his students' tests. (He's in his second year of teaching.) He had the occasion to curve a test recently and we used one of the methods listed. I won't say which, though! I can't tell you how useful this information will be to him should he need to employ any other methods. Thank you for your detailed explanations. Lori Dave, I don’t grade papers for a living but I do help my husband keep up with grading his students’ tests. (He’s in his second year of teaching.) He had the occasion to curve a test recently and we used one of the methods listed. I won’t say which, though!

I can’t tell you how useful this information will be to him should he need to employ any other methods. Thank you for your detailed explanations.

Lori

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