As you can see (by looking at the column "Obs"), both the Geometric and
Harmonic means ignore observations with LOS=0. If you think that those
observations can truely exist and are not some data error, than that
would be a strong argument in favor of the arithmetic mean.
If you think that those observations are data errors, then you should
ignore those observations anyhow, or try to recover their true value.
In those cases the choice between the different types of means can be
based on substantive reasons, see for instance (Avital and Falk 2006).
Hope this helps,
Maarten
Lann, Avital and Ruma Falk (2006) "Tell me the method, I'll give you
the mean", The American Statistician, 60(4): 322--327.
--- roland andersson <[email protected]> wrote:
> There are a total of 303 of 37736 patients with LOS=0. I looked for
> the different means in the two groups. Obviously the difference is
> largest for the arithmetic means and almost absent for the harmonic.
> Can you give an advice on what mean to use when reporting on LOS?
>
> -> lapscopiintention = 0
>
> Variable Type Obs Mean [95% Conf. Interval]
>
> vtid Arithmetic 28808 2.985178 2.924702 3.045654
> Geometric 28586 2.322214 2.304817 2.339742
> Harmonic 28586 1.931199 1.918483 1.944085
>
>
>
> -> lapscopiintention = 1
>
> Variable Type Obs Mean [95% Conf. Interval]
>
> vtid Arithmetic 8928 2.792451 2.745438 2.839463
> Geometric 8847 2.294519 2.26541 2.324002
> Harmonic 8847 1.933647 1.911211 1.956615
-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands
visiting address:
Buitenveldertselaan 3 (Metropolitan), room N515
+31 20 5986715
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
