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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