Re: More on: Re: [Gnumed-devel] First sample of gui function docs

[Tim Churches]

On Sun, 2003-08-17 at 09:07, Karsten Hilbert wrote:
> > I should have added that if a data item is null (not recorded), then a
> > label for that data item should not appear in the summary, so you don't
> > have a display of what information is missing...
> Not so in all cases: there's a difference between "allergy
> status unknown" and "no known allergies" but you knew that.

That's the difference between the use of systematic nulls and a mess.
When capturing information, it is vital to distinguish between "unknown"
and "nil/null". When collecting infomation to be used in aggregate
analyses, it is also important to further subdivide "unknown" into a)
"unknown because question not asked", b) "unknown because answer not
given by subject" and c) "unknown because answer not known by subject".
a) should be generally be excluded from the denominator when calculating
rates or proportions, but b) and c) should be included in the
denominator.

So yes, I was referring to data elements for which there are systematic
nulls. But you are correct, there are still exceptions, and it would be
worth displaying "Allergies: no information recorded" as well as
"Allergies: nil known".
-- 

Tim C

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