Tuesday, April 10, 2012

Grading for your homework 2

Hi all:
You will receive the grading for your homework 2 today. The maximal point is 81. Here are the stats:
- Undergrad: max = 60, min = 9, average = 37.6, stdev = 15.5 (excluding one student not submitting the homework)
- Graduate: max = 79, min = 37, average = 65.2, stdev = 10.4.

And here are the detailed points for each question and some observations that I have:

Question 1: totally 14
e, f: 3 each
g: 4 (1 for each heuristic)
h: 4 (2 for the mutex propagation, 1 for each heuristic)
Most of you did well for this planning question (some students however did not know the difference between a relaxed planning graph and a transition graph on the state space).

Question 2: totally 8
Soundness using truth table: 4 (you should be able to explain it correctly to get the full credits). Wrong explanation: -2
Completeness: 2. Wrong explanation: 0 (many students are confused between the completeness of an inference rule with the "equivalence" relation between two formula).
Resolution: 2

Question 3: totally 13
Propositional theory: 2
Clause form: 2
Resolution refutation: 3 for each. Total: 9
One mistake that I saw was that some students represented "mortal mammal" with a single proposition. Although with this KB, you can still prove/disprove the conjectures about "magical", "horned" and "mythical", doing so means that "mortal mammal" and "immortal" are two independent propositions, but apparently they are not.

Question 4: Totally 30
4.1 (Short answer questions): Totally 7
A: 3
B: 4 (2 for each question)
4.2 (Modeling the Springfield nuclear power plant): Totally 23
A: 5
B: 4 (1 point for the first two, 2 points for the last)
C: 3
D: 3
E: 8
Most of you did well in this question (however some student didn't even write Bayesian rule correctly for 4.1.A). For 4.2.C, many students used the argument that knowing "inferior plutonium" reduces the belief in "low quality heavy water" to claim that p3 < p1 (or the opposite), which is not true. It only means that p3 <= p2.

Question 5: Totally 16. Four for each part.
Many of you didn't convince me that you actually knew why P(AC) != P(A)P(C) for both 5a and 5c to get the full credits; fortunately the other two were easier. Also note that if you didn't actually try to prove these parts using probability and Bayesian rule, you won't get any credits.

Please let me know if you have any questions.

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