Comp210 Hw Grading Guide

Comp210 Labbies' Grading Guideline

To the Labbies

These are rough guidelines. Certain instances may have a higher or lower penalty at your discretion. If you're not sure about how to grade, ask me or john. Overall, I want grading to be relatively strict; 8/10 will be probably a decent score, and 10/10 rare.

If appropriate, give
 - data defn                  (-25%)
 - examples of data           (-25%)
 - template                   (-30%)
Use helper functions          (-50%)
  rather than one
  large unwieldy func
  (see below)
Every function needs
 - contract                   (-10%)
 - appropriate use of         (-10%)
   types (see below)
 - comments,                  (-25%)
   if args or return val
   isn't obvious from the names
 - to follow template         (-30%)
 - test cases                 (-25%)
   (After hw3, this will be
   optional for functions
   which are one short line.)
 - good indentation           (-30%)
   (incl. spacing)
 - no magic numbers           (-10%)
   (see below)
Papers must be stapled        (-10%)

Clearly, these add up to >100%. The point is, you can do many things wrong, which cause you to lose points. 'Course, you can't get negative on a particular (top-level) problem, but you may get zero for missing a 3-4 of the above items.
These are guidelines. Do not spend time doing a bunch of arithmetic, calculating 30% of 4 points, etc. Instead, mark things that are wrong, and keep a rough, gestalt idea in your head of how many points taken off, putting down just the final total. You can give partial-points for individual (top-level) problems, but the final score will be rounded up.
Of course, some problems may not fit the above: If the entire problem is "Write a data definition", then obviously that's more than 25%. Moreover, on early assignments we might be stressing the data definitions more than 25%.
Take off points for things that are wrong or ugly, but not otherwise listed here. (E.g., -1 for atrocious spelling throughout.)
By itself, "It works" does not merit any points. The point of this class is not to solve the homework problems, but to build general problem-solving (programming) skills.
Don't worry overly much about consistency: it's not possible to grade 60 papers and make sure you've graded them all the same, and still maintain sanity. There are many hw's over the semester, and consistent good work will end up with a good grade, despite occasional glitches.
If there is any extra-credit, list those points seperately.
Initial the papers you grade.
To the student
First, an explanation of a few items in the guide.
- "Use helper functions" is a matter of taste. The sin is to feel that you have to do everything in one big function -- that is no way to decompose a problem into simple parts! As a rule of thumb, a Scheme function shouldn't be more than ten lines or so of code, and will usually be five to six lines of code. As a general rule, if you are thinking in your head "these three lines compute the fluttershushanuff", then pay attention to the fact that your own thinking gives "fluttershushanuff" its own name; why not reflect that in your program? It's not unusual to have many small one- and two-line functions, just because they are obviously their own task.
- "Appropriate use of types" means (e.g.) using booleans for yes/no values, rather than using 0 and 1, or 'yep and 'nope. Later in the semester it includes using structures as needed. Overall, this point is not a big issue in Scheme.
- Magic numbers are constants hard-wired in the code. For instance, using "80 (mph)" instead of giving the concept a name like Cruising-Speed. Sometimes it is forgivable if that concept is used only once in your program (say, 60min/hr), but NEVER if it is used twice. (The only exceptions: 0 and 1.) For instance, in missionaries-and-cannibals (hw~6), the constant "3" should only occur once, in a define, and nowhere else.
- In the test cases for functions, we'll assume that any answer you list is the result of testing, and is what your function actually returns. If your function returns an incorrect answer, please note this in your comments.
Keep in mind that your labbies are grading a large number of papers, and sometimes mistakes are made. If you feel something was marked off even though it was correct, by all means check with the grader. However, if you feel that the grader was correct in taking off some points, but you feel they took off too many, try to defer to their judgement. If you feel that you've been graded overly-harshly consistently over several homeworks, first see the grader(s), and if they don't immediately agree, come see me (ian). (I've instructed the labbies to not change their previous judgement calls unless they are obviously way out of whack; I'll fix any accumulation of small judgement calls myself.)
Disclaimer: This guideline is not binding; we reserve the right to give whatever score we feel is fair.
Guarantee: You have the right to question any score, and get an explanation of why we feel it is fair.
See one of the instructors (ian or john) if you are unsatisfied with a grader's explanation.

Comp210 Labbies' Grading Guideline

To the Labbies

To the student