From: es2q+@andrew.cmu.edu (Erik Warren Selberg)
Newsgroups: soc.college
Subject: Re: fraternities
Date: 15 Apr 92 15:50:32 GMT
	<1992Apr15.015326.29506@midway.uchicago.edu>
Distribution: na
Organization: Junior, Math/Computer Science, Carnegie Mellon, Pittsburgh, PA

thf2@ellis.uchicago.edu (Ted Frank) writes:
> In article <sdusExq00VpKM8=J4f@andrew.cmu.edu> es2q+@andrew.cmu.edu (Erik Warr\
> en Selberg) writes:
> For the same reason we can say that smoking two packs a day makes you
> Y number of times more likely to get lung cancer.  Ceteris paribus,
> being in a fraternity makes you X number of times more likely to commit
> rape.

Not quite.  As mentioned in a previous post, there are several
different types of cigarettes, as there are several different types of
fraternities.  The general statement "Smoking two packs a day makes
you Y times more likely to get lung cancer" isn't necessarily true.
Ceteris paribus, The general statement "being in a fraternity makes
you X number of times more likely to commit rape" isn't necessarily true.

> >No, reuptable firms, professors, and committees (a) make mistakes and
> >(b) aren't necessarily modeling the true state of things.  I happen to
> >know a statistic that says in 1990 Utah spent the highest percent of its
> >local income tax on education.  This might imply that Utah spent the
> >most on its students, that it had good schools, or all sorts of
> >things.  The truth is it did, but because Utah has so many students,
> >it ends up spending the LEAST AMOUNT PER STUDENT in the 50 states.
> >But the original statistic still sounds like a good supporting
> >argument for why you should move to Utah.
> 
> Good logic.  You know of one statistic that can be misused, therefore
> all statistics are misused.  Talk about overgeneralizing.  

No, the logic here was I know of one statistic that can be misused,
therefore the possibility exists that another statistic can be
misused.

> Perhaps you can show why the X-times-likely statistic is invalid, rather
> than dismissing it out of hand?  You did such a wonderful job with that
> Utah statistic, you should have no problem with this one.

Using this statistic (copied from some other post):

From,   U.S. News and World Report ``When sex is the issue.'' 
        v 111 pages 34+ Oct 7 1991      

        ``A 1990 study by the University of Illinois at Urbana-Champaign
        concluded that 34 of the 54 reported sexual assaults were by
        fraternity men, even though they represent just a quarter of
        male students on campus.''

now, this statistic says that any given rape at UI-UC has a .62
(34/54) probability of being by a fraternity member.  This statistic
by itself doesn't mean much -- what you want first of all is the
confidence interval, using H0 = E[rapist is a fraternity member] ==
.62.  (if some stats god out there could figure this one out, I'd
appreciate it).

How can this statistic be misused?  Well, first off, we only know of
_reported_ rapes.  There was a nice post earlier on about that.
Second, the statement states they were "reported sexual assaults"
rather than "people convicted of a sexual assault."  Thus this
statistic is not too useful for determining my inclination to commit
rape, just the inclination of someone for percieveing it as such.
Finally, we'll just assume that 62% of the rapes at UI-UC are indeed
committed by fraternity members.  What does this say about Carnegie
Mellon?  not much -- it's kind of like getting stats on young male
drivers from the USA and using those statistics on youg male drivers
in Germany.  There isn't necessarily any correlation.


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