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CSC 165            Homework Exercise 1 -- Marking Scheme        Winter 2009
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NOTE TO STUDENTS:

You will find below the marking scheme used for your homework, including
the meaning of marking codes and number of marks associated with each one.
This file also contains my instructions to the marker (so you can get an
idea of how the homework was marked) and the marker's comments about each
question.

Please take the time to read this carefully before you ask questions about
the grading of your homework.


NOTE TO MARKER:

Be picky!  On any homework, it is the responsibility of students to show
that they understand how to solve each problem and to write up their
answers carefully.  At the same time, keep in mind that exercises are worth
only 2% of the final grade, so your marking should be somewhat coarse.  And
remember that marking is not only about evaluating a student's performance,
but also mostly about giving them feedback so that they can learn from
their mistakes.  This is especially important for students who made
numerous or more serious mistakes, as they are likely to need more feedback
in order to understand why their answers were incorrect.

For each question, I list solution elements with an associated code for
writing on student papers (the letter(s) between underscores _) and a
number of marks.  There are also general errors (with associated codes)
given below, with a maximum number of marks to take off for each type of
general error (as a percentage of the value of the question).  You will
likely encounter other common errors, or maybe decide to break down the
marking scheme further.  Simply make note of these changes/additions to
the marking scheme, and introduce new code letters (or short words) to
allow you to quickly give accurate feedback to the students (both in terms
of what they did wrong and how many marks it cost them).  Your marking
comments will be included in this marking scheme and posted on the course
website so that students may look up the meaning of marking codes and
understand how their work was marked.


GENERAL ERRORS (marked negatively, in addition to any other errors):

    _N_otation [up to 20%]:  incorrect/ambiguous notation

    _V_agueness [up to 20%]:  incorrect/unjustified/vague claim


1.  [12 marks]

    For each statement:

     .  1 mark for talking about the number of required program tests

     .  1 mark for justification/stating which tests could be done

     .  1 mark for the correct evaluation of the statement (True/False)

    Marker's Comments:


2.  [8 marks]

    For each statement:

    _T_rue [1 mark]:  correct diagram to make statement true

    _F_alse [1 mark]:  correct diagram to make statement false

    Give full marks for diagrams that show all possible regions with
    programs put in, leaving some regions suitably empty (like in the
    sample solutions), and also for diagrams that show explicitly the
    correct subset relationships (drawing some sets directly as subsets of
    others instead of showing all possible regions, even without any
    programs explicitly put in).

    Note that the original version of the exercise handout incorrectly
    defined J to be the set of all *Python* programs.  Be on the lookout
    for answers based on this notation and give them full marks, i.e.,
    nobody should lose marks if they use J *consistently* to denote the set
    of Python programs -- of course, answers that use J in an inconsistent
    manner without explaining what they are doing should lose marks.

    Marker's Comments:

    Code: U

    - For students who would benefit from stating where the programs belong
      in the Venn diagram.

    - A lot of students had a hard time specifying empty and non-empty sets
      without this.

    A bunch of students used either a logical not operator in their Venn
    diagrams or explicitly defined a "Python" set and an "Incorrect" set.
    I deducted 2 marks for doing either of these and then tried to evaluate
    their diagrams.