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AW: st: RE: A modest proposal - missing data doesn't count


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   AW: st: RE: A modest proposal - missing data doesn't count
Date   Tue, 15 Jun 2010 12:53:27 +0200

<> 

So, Allan, of course society could adopt the view that more traffic lights
are desirable, but the cost/benefit-tradeoffs have led to the current state
of affairs. The same thing happened with Stata: More warnings would prevent
more beginners from doing stupid things, but would also be a hassle for
advanced users.

I found the alternative approaches to missings presented in
http://www.stata.com/meeting/uk08/KIMacD.presentation.ppt wholly
unconvincing and worse than the current state. 

A traffic light does not stop you by itself, it merely tells you to stop. In
the same vein, the problem of missings being regard as bigger than other
numeric values has been appropriately flagged ([U], sect. 12.2.1. or
http://www.stata.com/support/faqs/data/values.html) and discussed frequently
on the list. You have to take the appropriate action yourself, though. Also,
commands such as -inspect- can tell you beforehand whether missings will be
an issue for you and you should consequently be on high alert...


HTH
Martin


-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Allan Reese
(Cefas)
Gesendet: Dienstag, 15. Juni 2010 11:34
An: statalist@hsphsun2.harvard.edu
Betreff: Re: st: RE: A modest proposal - missing data doesn't count

Thanks for all comments.  I'll continue to add -& x<.- to expressions as
-& !mi(x)- requires more typing and -inrange(x,10,.)- excludes the
missing but implements >= not >.

The fuss (addressing Martin's criticism) is that Stata has always been
consistent and logical# on this matter, but Stata users are not
consistent and logical - they're human.  Hence this issue is a pitfall
and I would love to find a way to make it less error prone.  Martin may
get it right every time; other users will not.  Many users of a certain
spreadsheet - or generally, managers of staff who use it - have assured
me, "If people enter the right values, then there is no problem."  If
people always did the right thing, we would not have trains passing red
lights, swabs left inside patients after operations, oil pipe valves
that fail to failsafe ...

It's so easy to forget that x<10 will not be affected by missing values
but x>10 will be.  It would be good to have software that guards against
pitfalls rather than invites you in.

Allan

# Computer logical, but when x is missing x>10 is formally undecided and
the result should be missing.


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