"New CS 473": Grading Policies

• Graded homework and exams
• Regrade requests
• Final course grades
• Past grade distributions
• Why I stopped dropping exam scores

If you have any questions or concerns, please ask in lecture, during office hours, on the course website, or by email.

Graded work

• Homeworks are graded by the course staff. In order to keep grading fast and consistent, all submissions for each numbered problem are graded by the same staff member. To keep grading fast, all required homework problems are graded on the following scale:
  0. Missing, not even wrong, or committing one of the Three Deadly Sins. (This score should be rare.)
  1. A good-faith incorrect solution, or "I don't know"
  2. On the right track, but with significant errors or omissions
  3. Mostly correct, but with a few minor errors or omissions
  4. Absolutely perfect. (This score should be rare.)
  Homework solutions may include more detailed 10-point rubrics, reflecting how we would grade each problem if it appeared on an exam. A score of n points on this 10-point scale corresponds to a score of ceiling(n/3) on the 4-point scale.
• Jeff will grade extra credit homework problems, most likely using stricter standards than regular problems. In particular, the "I don't know" policy does not apply to extra credit problems, and solutions must be at least partially correct (or creatively incorrect) to receive any partial credit.
• Graded homeworks and exams can be retrieved in office hours. Under normal circumstances, all work should graded and returned about one week after submission.
• Students can look up their homework and exam grades on the course Moodle site. We will also post exam grades on the course web page—just a sorted list of numbers, without names—so that students can see their relative standing in the class.
• Homework and exam solutions will be posted at most a day after the corresponding submission deadline. Exam solutions will include the rubrics used by the graders.

Regrade requests

• Please check that your grades are tabulated and recorded correctly. If you notice a mistake, please bring your graded work to Jeff or one of the TAs; we will correct it immediately.
• If you have any questions about your grade, please ask in office hours. However, except for arithmetic mistakes, no grades will be changed in the student's presence; all regrade requests must be submitted in writing.
• If you believe that your work has been graded incorrectly, please request a regrade in writing: resubmit the homework problem or exam with a brief written explanation of why you think your grade is incorrect. (For example, "My answer agrees with the posted solution." or "My grade does not match the posted rubric." or "My algorithm does not match the posted solution, but it is still correct." or "The posted solution is incorrect; here's a counterexample.")
• We can only grade what you actually wrote. You cannot get a higher grade by explaining what you meant. Modifying your homework or exam before asking for a regrade is an egregious violation of academic integrity policies, which will result in an automatic F in the course.
• Regrade requests must be submitted at most two weeks after graded work is returned. Except for arithmetic mistakes, late regrade requests will be ignored.
• If any posted solution contains a serious error, all students will receive a perfect score for that problem as extra credit. Yes, really.

Final course grades

1. Compute raw totals from homework and exam scores, excluding extra credit. Course work is weighted as follows:
   • 30% Homework: We will drop the six lowest problem scores.
   • 70% Exams: There will be two midterm exams, each worth 20% of your raw total, and a cumultive final exam, worth 30% of your raw total. We do not plan to drop any exam problems.
   • Exceptions: Any forgiven homeworks or exams will be treated as though they were never assigned; we will drop the same fraction of each student's unforgiven scores. On the other hand, we will not drop zeros that result from cheating offenses.

2. Compute adjusted totals, which include extra credit points. Extra credit points are not necessarily worth the same as regular points.

3. Remove outliers at both ends of the curve.
   • Anyone with an adjusted total over 95% automatically gets an A+. This rule typically applies to the top 2–3% of the class. I reserve the right to lower the 95% cutoff.
   • Anyone with an adjusted total below 40%, or who has submitted less than 50% of the homework, or who otherwise does not appear to be making a good faith effort, automatically gets an F. This rule typically applies to the bottom 2-3% of the class. This is not the only way to fail!

4. Determine letter-grade cutoffs from the undergraduate raw totals. Outliers and graduate students are excluded from the cutoff computation to avoid unfairly skewing the curve for undergraduates. The mean is the center of the B range, and each standard deviation is worth 3/4 of a letter grade. For example, the B+/A– cutoff is 2/3 standard deviations above the mean, and the B–/C+ cutoff is 2/3 standard deviations below the mean.

5. Compute final letter grades (for non-outliers) from adjusted totals.
   • In particular, grades for graduate students will be determined by comparing their adjusted total to the undergraduate curve.

6. Adjust grades upwards at the instructor's whim.

Past grade distributions

This course has never been taught before, but for comparison, here are rough statistics from the last five times Jeff taught CS 473. (See below for a possible explanation for the significant jump in 2010.) Here the mean was at the C+/B– boundary, and each standard deviation was a full letter grade.

Semester	Mean ± stdev	Min pass	#As	#Bs	#Cs	#Ds	#Fs
Fall 2006	65% ± 11%	40%	25	26	23	13	5
Spring 2009	66% ± 13%	43%	21	25	26	14	2
Spring 2010	72% ± 12%	47%	24	34	35	16	3
Fall 2012	71% ± 13%	44%	36	51	42	33	2
Fall 2013	73% ± 11%	50%	49	58	55	19	2
Typical	72% ± 12%	47%	24%	30%	28%	15%	3%

Here are rough statistics from the previous offerings of CS 374. Again, the mean was at the C+/B– boundary, and each standard deviation was a full letter grade. The averages were significantly lower than in CS 473, but this reflects changes in grading standards (and the novelty of the course) more than the abilities of the students.

Semester	Mean ± stdev	Min pass	#As	#Bs	#Cs	#Ds	#Fs
Spring 2014	59% ± 11%	38%	8	11	8	8	1
Fall 2014	62% ± 12%	38%	16	22	22	12	0

Why I stopped dropping exam scores

In 2010, I switched to a policy of dropping the lowest three three exam problems across the entire semester. With this new policy, the strategy of ignoring one problem on each exam virtually disappeared; surprisingly, this lead to a significant improvement in overall averages! See the statistics above.

However, dropping the lowest exam scores actually lowers more grades than it raises, because of more subtle statistical effects. Dropping scores raises everyone's average (as a percentage of the maximum possible score), which means it also raises the mean. If you have mostly high scores with a few low outliers, dropping the low outliers raises your average. But if all scores to be about the same, dropping the lowest scores actually lowers your average relative to the rest of the class.

So now we just keep it simple. Every exam grade counts.

I drop homework scores for a different reason — sometimes students get sick or overwhelmed, or they need to travel, but the class is too complex to reliably deal with extensions. Homework scores are typically high enough and their contribution to the final course grade is low enough to avoid any counterintuitive statistical effects. Or so I tell myself.