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When grading problems on quizzes and exams, I often break them down into sub-problems, each worth a portion of the total points. I use rubrics to award partial credit for each sub-problem. However, this practice leads to students arguing that their incorrect work deserves more partial credit than what I gave them. For example, a student might claim that their mistake only warrants a deduction of 0.1 points rather than the 0.3 points I deducted.

To avoid these disputes, I'm considering switching to a binary grading system where each sub-problem is graded as either completely correct (full points) or completely incorrect (zero points), with no partial credit awarded.

My questions are:

  1. Do you award partial credit when grading, or do you use a binary grading system?
  2. If you do award partial credit, how do you justify and explain the specific point deductions to students who argue that they deserve more partial credit?
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    $\begingroup$ "To avoid these disputes ..." --> A memorable professor I had would re-grade one's work if the student felt something was amiss (like skipped pages in the review, incorrect assessment, questionable grading, etc.). Yet the entire assignment was re-graded, not just a portion. Often possible to get a lower score on the re-grade. $\endgroup$ Mar 7 at 1:52
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    $\begingroup$ My professor for who I as a teaching assistent: only argue with students if there was a clear misstake (e.g. points not tallied correctly) or they make a valid point. As a grader you make an effort to grade fairly. That is your justification for the partial credit. There is only a certain "resolution" (precision?) you can achieve with grading, because of how complex it is to accurately give points to a piece of human written text. If you want 100% fairness, you should stick to multiple choice questions. But that is far from ideal for obvious reasons. $\endgroup$ Mar 8 at 9:17

7 Answers 7

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Is it a good idea to give partial points in grading?

In my opinion, yes because it makes the grading more fair.

Do you give partial points when you grade?

Yes. I set a criterion and adapt it according to unexpected errors that appear (for example: -0.1 if it is a small error; -0.5 if half is right; 0.1 if almost everything is wrong; -0.2 if there is an error X which I didn't even imagine). This criterion is explicitly presented to students.

How do you justify how much points to deduct when students come to argue for more points?

I use the criteria I presented to them (I usually make printed copies available): these are the points because this is what the criteria say.

Also (and this is very important), I tell them upfront that:

  • the same criteria were applied to all students equally.
  • I will only change the grade if they detect an error in the way the criteria were applied (which eventually happens).
  • If they don't agree with me, they can appeal under the terms of the regulation (in this case, the department would set up a commission to decide, but that never happened to me).

In summary, in my experience, the most important thing to avoid complaints is to be completely clear about the criteria (what the points are for each part of each question) and to apply them uniformly (equal errors should receive equal scores).

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  1. I always allow the possibility for partial credit. Unless the problems are quite simple, there will be a good amount of room between a perfect solution and a solution that deserves no credit. If you don't take this into account, you lose a lot of the information that grading is supposed to capture, e.g. the difference between a student who knows nothing vs. a student who implements the right overall idea, but with errors, vs. a student with a perfect response.

  2. Students often ask for more points, this is part of teaching. My policy on such requests is: if I have made a clear error in grading your work, such as a misreading or misunderstanding of what you wrote (which does happen sometimes), I'll give you the points back. But I won't revisit judgment calls about how much partial credit a response deserves. This policy is easy to apply, and easy to justify on fairness grounds: reconsidering partial credit for one student who happens to complain is not fair to the other students who may have made similar errors (often, the exact same error) but didn't complain. I have used this policy for a long time, and have never had a problem with it. Students might not be happy, but once they see I won't budge on this, they stop bothering me with meritless requests for more credit.

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    $\begingroup$ Consistency is key. If two students make the same error and receive different judgment calls, they may feel that the grading is unfair. Mind you, OP uses rubrics, which mostly eliminates this issue. $\endgroup$
    – Brian
    Mar 6 at 16:18
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    $\begingroup$ @Brian The judgment call is about how many points to take off for a given error. Of course, once this judgment call is made, I am careful to apply it consistently, as anything else would be flagrantly unfair. $\endgroup$ Mar 6 at 16:32
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In my experience, binary credit on sub-problems is the way to go. Once you open the door to interpretation on partial credit, you get your time burned by pointless debates (pun intended) with adversarial students.

But the thing is, you have to make sure that the sub-problems are

  • sufficient in number, so that there is room to make a few mistakes on the quiz and still get a good grade, and

  • sufficiently atomic, so that it feels reasonable to grade them on a binary scale.

The goal is for the grade calculation to be totally obvious and feel fair enough that the student doesn't argue against its mechanics.

In this way, grade calculations are like laws: you want them to be both clear and fair. If you have unclear laws then people will waste your time in court arguing about interpretation. If you have unfair laws then you'll hurt good people and people will rebel against you.

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    $\begingroup$ I like the "atomic" criterion. My experience is that when people are debating over partial points, it means you haven't used the right scale to capture that atomic concept. $\endgroup$
    – pjs
    Mar 6 at 16:39
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    $\begingroup$ Keeping grading as fair and transparent as possible is important for reinforcing a growth mindset: if students can't figure out what a score is measuring, they'll fall back on assuming it's a direct assessment of them/their intrinsic (immutable) ability level. $\endgroup$
    – TomKern
    Mar 6 at 22:48
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I use a binary grading system.

A few tips to help students accept a partial-credit-less grading system:

  • Offer full credit if the student makes a mistake that does not affect their demonstration of the assessed learning outcome (e.g. arithmetic error)
  • Tune your assessments to make up for the dip in grades due to the missing partial credit. Usually this means lower complexity questions. The real advantage of binary grading is that it makes it much easier to assess an assessment: "I expect a B student to definitely be able to get these questions correct, and maybe half of these questions correct, so they'll probably get somewhere around this grade, which should be in the middle of the B range". Don't be afraid to err on the side of generosity.

If you want to be really generous with your time, you can also make up the dip in grades by offering retakes. Retakes synergize well with binary grading, since:

  • Binary grading is much faster to balance the extra time grading retakes
  • Students are less likely to retake a question the more partial credit they have on it
  • Students are less devastated by missing out on getting any points for a question if they can retake
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There are lots of good answers already, but I'll add one thing that works from my experience: add points, don't subtract them.

Polya's principles include understand the problem, devise a plan, and then carry out the plan (the fourth, look back, doesn't necessarily apply to summative exam questions). So I'll award ~30% of the credit for evidence that they understood the problem. For instance, a decent picture, or writing facts or theorems that are relevant. Then ~40% for carrying that understanding through to a strategy for solution, for instance, an integral that needs to be evaluated. Then final ~30% is for carrying out that strategy.

These criteria aren't independent, of course. A flawed strategy for setting up an integral may lead to on that can't be evaluated in elementary terms. But scoring with these benchmarks in mind shifts the discussion from “How many points did you lose for doing things wrong?” to “How many points did you earn for doing things right?”

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Another reason I like partial credit on tests is it reduces student nervousness. They may have the right approach but be completely stuck bringing it home. With partial credit they know they got those points and can move on, coming back if there's time. Without, they can spend far too much time banging their heads, or checking each question is perfect.

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I not only award partial credit when grading, but I actively encourage the students to "dispute" it and I guarantee that the grade won't be decreased after review. I've been applying this system for 8 years.

Teaching doesn't end when the exam starts, and the exam is not only a tool for sorting students as either failing or passing. If the student fails, they will retake the exam, and they have to know how bad they did. A mark of 15% is different from a mark of 50% even though both result in the student failing the exam. Some students think they know the subject better than they really do. A very low mark tells them otherwise, and partial grading allows me to convey meaning within the not-pass range.

Partial credit also allows me to distinguish between minor errors and fundamental misunderstandings of core concepts. For instance, a student may receive a better grade for a full page of work with minor mistakes than for page where a single line overlooks a crucial topic covered extensively in class. As a professor, it's important that the student knows which topics are crucial (well, I talk about that repeatedly during the course, but they put more attention after they failed the exam, and they put even more attention when they are trying to plea)

In practice, many students will neither dispute the grade nor request clarifications. Those who do, usually request clarifications without disputing the grade. There are few cases where a student actively attempts to improve their grade, or even convert a fail to a pass.

Very few students require an itemized detail of their grade (as in how many points were deducted by each mistake). If they ask for it, I'll deliver. Usually they stop me midway "Ok, I get it". If they insist that the grade is not fair, it's always possible to ask another professor for an opinion (which, in my experience, is hardly even needed)

If they honestly have no clue about why the mark was so low, or they know they did poorly and they're just trying to game the system, the answer is straighforward: "it was a crucial mistake, we talked a lot about that in the lecture of <date>, see exercise of the book." and the "dispute" doesn't take long.

If I cannot provide an explanation, or they present a convincing argument, then it's clear that it was my mistake in one way or another.

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