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Subject:  Midterm Exam Answers & Statistics
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The midterm answers and grading scheme are posted at:

http://www.cse.buffalo.edu/~rapaport/191/F09/Private/mt-ans

with the usual username and password.

Midterm Exam Statistics
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Total possible points = 63
Grade range = 28 (D+) - 63 (A)
Computed Average = 45.5 (B-)

Distribution of grades:
  A   4
  A-  8     total A's: 12
 
  B+ 10
  B  17
  B-  4     total Bs: 31

  C+ 12     total above defined average = 55
  C  22		
  C- 16     total Cs: 50

  D+  1	    total Ds:  1
            total below defined average = 51

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The biggest thing I noticed was the large number of students,
approximately the same number as those who don't attend lecture :-), 
who did not have the foggiest idea how to represent an English sentence
in FOL or how to even begin to prove a theorem.  

For example, I could easily distinguish between:

* students who knew what they were doing
  (even if they only got partial credit on a problem);

  such a student might get the problem right or might err in the
  following way:  e.g., representing "all dogs are animals" as:
        Ax[Dog(x) ^ Animal(x)]
  which is semantically INcorrect (it means that everything is both a
  dog and an animal!), but at least is syntactically correct

* students who had a vague idea of what they were doing
  but got the problems completely wrong;

  such a student might have represented "all dogs are animals" as:
        D -> A
  which isn't even FOL (it's propositional logic, sort of)

* and students who seemed completely clueless; many students did
  something analogous to representing "all dogs are animals" as:
        m + n = even
  which doesn't even make sense mathematically,  or
	All(Animals(Dogs))(x)
  which is also syntactically impossible.

It's clear that that last group of students (who tended to get Ds or
low Cs on the midterm) are not attending lecture, not reading the text, 
and/or not doing more than the bare minimum (if that) in the course.
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Fair warning: the course gets harder as the semester progresses!

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You will have plenty of opportunity to improve your grades during the
rest of the semester via HWs and the final exam.

In addition, I will make the following offer:  If your final-exam
grade is higher than your midterm grade, then I will replace your
midterm grade in the final grade computation by your final-exam grade.