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From: frank@grep.co.uk (Frank Wales)
Newsgroups: comp.software-eng
Subject: Re: metrics and the SAT example
Message-ID: <1991May28.144418.6332@grep.co.uk>
Date: 28 May 91 14:44:18 GMT
Article-I.D.: grep.1991May28.144418.6332
References: <24563@unix.SRI.COM> <1991May21.223401.27023@netcom.COM> <1991May22.222646.10571@ico.isc.com> <1991May23.014904.5896@netcom.COM> <1991May24.192101.22317@grep.co.uk> <1991May25.053304.10445@netcom.COM>
Reply-To: frank@grep.co.uk (Frank Wales)
Organization: Grep Limited, LEEDS, UK
Lines: 41

JS == jls@netcom.COM (Jim Showalter) == JS:
ME == me:
ME>It must be possible to establish credible causality too, otherwise you
ME>can't be sure what you're measuring.  Say you notice that levels of 
ME>ice-cream consumption correlate strongly with deaths at the beach.
ME>Does this mean ice-cream is a killer?

JS>Not at all. But it DOES mean ice-cream is a good predictor for
JS>beach-deaths, which was precisely my point. Thanks for providing another
JS>example to support my thesis! :-)

"It's dead, Jim!"  :-) Beach deaths are already an excellent measure of
beach deaths.  There is little point in obtaining others unless they buy
you something; for example, insight or understanding.  My concern here
is not with whatever other auxiliary numbers can be obtained that mean
the same thing as the original statistics; it's what people *do* with
these other numbers, and especially what they attempt to intuit from 
the relationship between them.  For example, if people attempt to cure the
"beach-death problem" by restricting ice-cream sales on the basis of
these data, they've only bought disappointment and frustration.

More to the point, such bogus applications of non-causal correlations
undermine similar, perhaps more valid, measures, and that is a real cost;
for a start, it makes it harder to convince people of the value of metrics.

JS>My father pointed out one time
JS>that the statement "it only provides symptomatic relief" was stupid: if
JS>the symptoms of a broken arm are pain, bone jutting from muscle, and an
JS>inability to lift objects with the arm, then relieving those symptoms
JS>is the same as curing the problem--so what's the objection?

ME>I take it your father wasn't a doctor, then? :-)  Taking Tylenol whenever
ME>you have a headache doesn't cure your brain tumour.

JS>My dad was only pointing it out for broken arms. It doesn't work for
JS>everything.

Indeed.  Like helping to 'cure' ailing software projects, for example.
--
Frank Wales, Grep Limited,             [frank@grep.co.uk<->uunet!grep!frank]
Kirkfields Business Centre, Kirk Lane, LEEDS, UK, LS19 7LX. (+44) 532 500303