
Assignment 2 marking.

Solutions are posted on the SFU vault.
I will post them on Canvas Tuesday (Feb 2nd) morning around 9am.

Please mark the following 5 questions, 2 marks each.
You can give half marks.

Michael Monagan


Textbook questions

o Section 11.2 Exercise 9 part (a) only.  See Figure 11.29 on page 529.
   They MUST give a reason for why the two graphs are not isomorphic since
   the book says "No" they are not isomorphic.
   Probably most students will say that they have a different number of 4 cycles.
   The first graph has two 4 cycles, the second has three 4 cycles.

o Section 3.6 Exercise 2
   There are two probabilities to be calculated.
      Pr(A|B) = 0.75   and  Pr(A|Bbar) = 0.5 
   To calculate these they MUST first determine  Pr(A intersect B) = 0.3
   If they don't have that give them 0 -- they must have copied 
   their answer from somewhere.  Don't be afraid to give 0 for no working.

   Give 
   1 mark for Pr(A intersect B)
   1/2 mark for Pr(A|B) and 
   1/2 mark for Pr(A|Bbar).

Instructor questions

Q4 Mark (b) and (c) only  1 mark each
   For part (c) it is sufficient to say "No because two isomorphic graphs must
    hae the same number of edges and K6 has 15 edges which is odd."

Q8 Give 1 mark each for part (a) and part (b).
   They need to show some working.

Q12 The COVID question.
   They need to calculate 
     Pr( that an American tests +ve ) = .10 x .98 + .9 x .03 = .125  then
     Pr( has COVID | tested +ve ) = .92 x .10 / .125 = .784
   Just look for those two numbers -- .125 and .784  (1 mark each).

You don't need to write any explanations for your marking.
Just put an X where they did something wrong.

If they did not include a cover page penalize them 2 marks this time.
Write : Missing cover page - 2 marks.

Michael Monagan
