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CSC 236            Homework Exercise 6 -- Marking Scheme          Fall 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 and your marking time is very limited, so your
marking must be coarse -- unfortunately, you do not have time to make fine
distinctions, so do not give or take away anything smaller than 0.5 marks.
Be on the lookout for misinterpretations of the question and don't take off
too many marks for making incorrect but reasonable implicit assumptions --
of course, this is open to your judgement about what is "reasonable", but
that is one area where you should be more lenient.

Also, remember that marking is not just about evaluating the students's
performances, but also about giving them feedback so that they can learn
from their mistakes -- within the limitations imposed by your marking time,
of course.  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).  Please record any
such marking codes or common errors below.

For solutions that are significantly different from the expected, just use
the following basic general breakdown of marks:

    _F_ormat [roughly 33%]:  proper format/structure for the answer,
        independently of the solution's correctness

    _I_dea [roughly 33%]:  correct high-level idea/intuition for the
        answer, independently of the format or details provided

    _D_etails [roughly 33%]:  each part of the solution is provided and
        correct, independently of the format


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

    _A_rithmetic/_A_lgebra [up to 10%]:  calculation error

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

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


OVERALL:

    Take off up to 1 mark globally for bad use of notation (using code _N_
    above), in increments of .5.  But try to mark the correctness of each
    question independently from the notation -- unless the notation is so
    far off that it affects correctness, or makes it impossible to tell.


1.  [2 marks]

    _C_orrectness [1 mark]:  L(A_1) = L_1, even if this fact is not
        justified [.5 marks for each inclusion]

    _J_ustification [1 mark]:  reasonable justification


2.  [2 marks]

    _C_orrectness [1 mark]:  L(A_2) = L_2, even if this fact is not
        justified [.5 marks for each inclusion]

    _J_ustification [1 mark]:  reasonable justification


3.  [2 marks]

    _C_orrectness [1 mark]:  L(A_3) = L_3, even if this fact is not
        justified [.5 marks for each inclusion]

    _J_ustification [1 mark]:  reasonable justification


Marker's Comments / Error Codes:  See individual comments on your paper.