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SUBJECT:  POSITION PAPER 2 STATISTICS
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1.
I have finished grading PP2 and will hand it back on Wednesday.

The points ranged from 12 - 24 (C- to A),
with a class average of 18.4 (B-).

So, you did better (on average) than for PP1, though some of you did
much better, while others didn't.

Once again, some of you lost points for improper citation styles
or not handing in your peer-edited first drafts.

Once again, if you want to gain back those lost points,
please fix your citations or hand in your peer-edited first drafts
(or both).

This continues to apply to PP1 (no one has yet taken me up on that offer!)

And, once again, there will be an opportunity for you to revise one of
your position papers at the end of the semester.

Of course, if you have questions about your grades, please ask me.

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2.
The biggest problem concerned your evaluations of the validity of the
arguments and your agreement/disagreement with the conclusions.  
Many of you seemed to pay more attention to the premises.

Almost all of you ignored the fact that there were *two* arguments; 
you said things like, "The argument is valid."  or "The argument is
invalid." 

But there were two arguments:

	1...4/.'.5
and	5/.'.6

So you had to say whether *each* was valid or invalid,
and you had to say whether you agreed with *each* conclusion.
(This was clearly spelled out in the grading scheme that I posted!)
(Which, to remind you, is available from:
http://www.cse.buffalo.edu/~rapaport/584/S10/pospapers.html
or, more directly, at:
http://www.cse.buffalo.edu/~rapaport/584/S10/pp2grading.txt

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3.
A related issue some of you are still not clear on is the relation of
one valid or invalid argument to another.  

If you have two arguments such that the conclusion of one is a premise
of the other (as is the case with the two arguments of PP2),
the question of the validity of one of them is *independent* of the
question of the validity of the other.

Here's an example:

Arg 1:  All cats are animals                (true)
        Tweety the bird is an animal        (true)
        Therefore, Tweety the bird is a cat (false)

Arg 1 is invalid (because it's clearly possible to have all true
                  premises and a false conclusion)
(and therefore it is unsound) 

Arg 2:  Tweety the bird is a cat            (false)
        All cats fly                        (false)
        Therefore, Tweety the bird flies    (true)

Arg 2 is valid!
(...because if Tweety is a member of the class of cats,
    and if the class of cats is a subset of the class of flying things,
    then Tweety is also a member of the class of flying things;
    that's simple set theory)

The fact that one of its premises is false is irrelevant to its validity.  
So is the fact that that premise was unsoundly inferred in Arg 1.  

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4.
And, of course, there's the issue of getting terminology straight,
which I emailed you about earlier.  Let me say a few more words
about this:

A common mistake was to say "conclusion (5 or 6) is invalid", which I
took to mean "conclusion (5 or 6) does not follow (from the preceding
premises)".  And people who did something like this *and* said whether
they believed/disbelieved the conclusion got at least partial credit
despite the terminological problems.
(But please pay attention to this on PP3.)

However, if you *only* wrote something on your paper like "conclusion 5
is valid (or invalid)" and did not state whether or not you believed
conclusion 5, then you *must* have missed one of the components of what
you had to do.  

If you meant "true" by 'valid', or "false" by 'invalid', then you
stated your belief but did not assess validity.  

If you meant the "argument ending at conclusion 5 is valid"
or "the argument ending at conclusion 5 is invalid",
then you assessed validity but did not state your
belief/disbelief in the conclusion.  

SO THIS IS NOT A MINOR TERMINOLOGICAL POINT
...and it can make the discussion around your conclusion seem very confused
...so please check for this in subsequent position papers.