I have made some simple corrections in the quiz for typos and other stuff.
In addition, my comments are:

Problem 1:  All good.

Problem 2: I think part a should ask for Hasse diagram (as it does),
not dependancy graph.  No one likes drawing dependecy graphs anyway

Problem 3: Perhaps ask people to explain their answer if it's TRUE and
give a counterexample if FALSE (right now it just asks for
counterexample for FALSEs).

Problem 4: 

1. Solution for b) should probably include a picture, since we ask for
   a picture in the problem.

2. Part d): dow we really want to have the students rewrite the entire
   false proof with just a single sentance change?  As it's stated
   write now, they would have to do that, and that's a lot of copying.
   Perhaps something like "explain how you would modify the false
   proof to obtain a correct proof of the new theorem" would be
   better.

Problem 5:  I like it.

Problem 6:  I like this one too!

Of course, six problem is probably too many.  I would recommend
dropping Problem 2.  If it's still too long, consider giving them the
invariant in 5c) and just asking them to prove that it holds.  That
should save them much time.  Problem 6 should be kept, of course.

Adrian.