This makes sense if time is a discrete variable
e.g. 5th-10th day where 5 refers to a full day and 10 refers to a full
day
total time= 6 days
It doesn't make sense if time is continuous.
e.g. 5th day midnight -10th day midnight
total time = 5 days.
Matt
-----Original Message-----
From: Joseph Coveney [mailto:jcoveney@bigplanet.com]
Sent: Wednesday, December 11, 2002 5:08 PM
To: Statalist
Subject: st: Calculating duration of time
Somewhere I had read that it has become a convention to define a duration or
interval
of time as:
end time - start time + 1,
where the 1 is the unit of time used. Thus, for example, for a common
health
economics measure, the length of hospital stay (LOS) is defined to be
discharge date -
admission date + 1 day.
A patient who is discharged a few hours after admission would have an LOS of
one
day, one who is discharged the day after admission would have an LOS of two
days,
and so on. I suppose that the motivation for this definition is to remove
zeroes from
durations, since these are often skewed and a logarithmic transformation is
used, as for
example -means LOS, add(1)-.
I thought that I had seen the formula in an online data definition document
or data
standards document at a website for the Center for Disease Control, FDA, HL7
or
CDISC, but I cannot relocate it. Apologies for the somewhat off-topic
nature of the
question, but has anyone on the list come across this convention?
Joseph Coveney
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