Posted by: jeff | October 6, 2010

HW2 (+ Q3 of HW1) Grades

I’m not going to sugar-coat it, statistically speaking, the grades for these 4 problems (HW1 Q3 + HW2 Q2-4, 115 pts. total) were not so good.

  • Mean Score: 41
  • Median Score: 46
  • Standard Deviation: 30

These figures include quite a few zeros from students who did not submit this assignment, some of whom may have dropped the class.  So the statistics for those of you who did submit your work would be higher.  As with the first assignment, the range of scores was very large (teens to 100+).

So what can we learn from this in order to improve in the future?  For one, your answers need to follow the grading rubric.  We post that so you have a clear indication of the point breakdown for each question.  If you don’t provide one part of the solution that’s described in the rubric (i.e. proof idea, description of a general instance, a specific example, etc.), you won’t receive any of the points that are allotted for that section; it’s just that simple.  A lot of solutions that I graded lost points needlessly for just not following the rubric.  I will be making an effort to post the rubrics even sooner after HWs are posted so you’ll be able to get a sense of how to format your solutions when you start. As always, we would encourage you to start at least thinking about the problems on the HWs as early as you can.

Secondly, the onus is on you to provide answers that convince Alex and I that you understand the concepts we’re trying to assess with these HW questions.  It is not our responsibility to decode cryptic answers, rather, it is your responsibility to submit work that is clear and direct, and that shows us that you know what you’re talking about.  Some of this is as simple as making sure your writing is legible (seriously), that you don’t have half of the page crossed out, and that your answers are in clear, complete sentences.  In other words, make sure your work looks like a college student (and not a middle school student) wrote it, and write your solutions so they are easy for another person (i.e. Alex and I) to understand.  Even if you truly understand the concepts, if we can’t understand your solutions, we’ll never know how much of the material you actually grasp.

Another point that I’d like to make ties in with both of these, and it’s regarding the “Proof Idea”, “Reduction Idea”, or “Algorithm Idea” sections you are asked to write.  I’m sure this has been discussed in lecture, I’ve discussed it in recitation, and you’ve now seen several examples of what should constitute your “Idea” sections in the solutions we’ve provided for previous homeworks.  Even our solutions are a bit wordy for what we’re looking for from you, because we’re trying to explain and put things in context for you when you read them, things you don’t need to do so much of in yours.  Any time you’re asked to write a “* Idea” section before you write the “*” section (where * is Proof, Algorithm, Reduction, etc.), you should present the main ideas only, and save the details for the “*” section.  In the ideas, less is more.  Think about boiling the whole thing down to the core insights that are driving your solution.  If you’re applying some algorithm from class to this new problem, say so, directly.  Maybe it needs some slight modifications to solve the problem at hand…provide us with the ideas behind those modifications (i.e. “do this one part of the algo. this way instead of that way”), but save the details (with math, notation, etc.) for the actual proof/algorithm/reduction.  So your ideas sections are how you would describe your approach to a classmate if you were talking to them and only had a few sentences.  This is not a hard restriction on length, but generally these won’t need to be very long b/c there are only a few separate ideas for each proof/algorithm/reduction.

Hopefully this post has helped to clear things up.  And if not, or if you have any other questions at all, you can always ask one of us (Alex, Atri, or myself) in lecture, recitation, email, office hours, online office hours, the comments section of the blog,…



  1. Isn’t it out of 115 points?

    • Hi Andy,

      yes, you’re correct. Thanks for catching that typo: I fixed it in the post.

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