From: mccall@mksol.dseg.ti.com (fred j mccall 575-3539)
Subject: Re: Good news for 2.0 and other Tidbits.
Organization: Texas Instruments Inc
Date: Thu, 1 Oct 1992 17:10:53 GMT

In <1992Oct1.004546.2871@muddcs.claremont.edu> jokim@jarthur.claremont.edu (John H. Kim) writes:

>mccall@mksol.dseg.ti.com (fred j mccall 575-3539) writes:
>>In <1992Sep30.092259.6407@muddcs.claremont.edu> jokim@jarthur.claremont.edu (John H. Kim) writes:
>>>philipla@microsoft.com (Phil Lafornara) writes:
>>>>In article <1992Sep28.232210.21615@muddcs.claremont.edu> jokim@jarthur.claremont.edu (John H. Kim) writes:
>>>>>
>>>>>He doesn't need evidence Phil.  A little logic will prove it.
>>>>>
>>>>>There are two sets of people.  Set A comprises those who want a
>>>>>product badly enough to buy it.  Say that of set A, 75% of the
>>>>>purchases are actually used.  Set B comprises those who don't
>>>>>want to buy a product.  Obviously, usage in set A is much greater
>>>>>than usage in set B, so we'll set B usage at 25%.  (These numbers
>>>>>are completely arbitrary, and I use them only to clarify the point)

>>>>     The flaw in your logic is the following:  You are taking as
>>>>an axiom the idea that usage in set B will always be less that
>>>>usage in set A.  I think you are probably correct - it would seem
>>>>like common sense to me.  However, there aren't any figures to
>>>>back up that assumption, which makes the rest of the (rather nice, 
>>>>by the way) proof specious at best.

>>>The proof for that axiom follows along the lines of the other proof.
>>>Set Y is people who want to use the software.  Set Z is people who
>>>don't want to use the software.  Set A is comprised entirely of people
>>>from set Y (else why would they buy the software?).  

>>Fine to this point.

>>>Set B is a mix
>>>of people from set Y and set Z.  

>>You can't assume this as a certitude, although I'd say it's a pretty
>>good bet.  Set B could presumable be an improper subset of Set A and
>>not actually include any people who don't want to use the software,
>>despite the fact that they did not actively acquire it (i.e., it came
>>bundled).

>>  The fact that Set B *MAY* contain people from Set Z does
>>not mean that it *MUST* contain any.

>In a strictly mathematical sense, you're right.  Since the entire set
>being considered is a union of A and B, if set B contains no members of
>set Z, EVERYBODY must be a member of set Y.  Sounds great up to here.
>Now translate that into the real world.  EVERYBODY wants that particular
>piece of software.  I think we can safely assume that isn't the case.

You've committed a logical error here.  You seem to be assuming that
if we take everyone in Set A and everyone in Set B that we now have
EVERYONE.  We don't know that.  We know that if we take everyone in
Set Y and everyone in Set Z that we have everyone, but we have no such
assurance with regard to Sets A & B.

>>Because one of your premises is falsifiable, your conclusion is
>>falsifiable (which I suspect is what Phil was getting at -- although
>>it'd be nice if the apparent results of logic training were applied a
>>BIT more even-handedly).

>One of the first things I learned in engineering was not to get trapped
>into thinking if it couldn't be done logically or mathematically, it
>couldn't be done at all.  Sometimes you have to make some assumptions
>which are entirely reasonable in the real world.  I will give you that
>in ONE case (the case you pointed out) my proof doesn't hold.  However,
>that one case is so unlikely that I think most people would agree it
>doesn't pose a threat to the conclusion.  Remember that the premises
>are based on the real world.

Nobody said it was LIKELY.  However, are you talking 'liklihood' or
are you talking 'proof'?

[I agree with you, by the way, but Phil's point is indeed valid.]

-- 
"Insisting on perfect safety is for people who don't have the balls to live
 in the real world."   -- Mary Shafer, NASA Ames Dryden
------------------------------------------------------------------------------
Fred.McCall@dseg.ti.com - I don't speak for others and they don't speak for me.