From Elizabeth.EBY@med.va.gov To statalist@hsphsun2.harvard.edu Subject st: adjusted percentages and adjusted odds ratios Date Fri, 19 Sep 2003 10:46:40 -0500

Hi-
Could someone help me out with understanding the relatively small difference
in adjusted percentages (20% vs 17%) compared to a more robust adjusted odds
ration of 1.7?  The adjusted percentages are controlling for covariates, and
were obtained using the predict sequence.

Thank you,

Elizabeth Eby
Research Health Science Specialist
Ann Arbor VAMC
734-769-7100 X6248

-----Original Message-----
From: Copeland, Laurel
Sent: Friday, September 19, 2003 11:28 AM
To: Eby, Elizabeth

I don't know. Maybe put the question to Statalist?

-----Original Message-----
From: Eby, Elizabeth
Sent: Friday, September 19, 2003 11:27 AM
To: Copeland, Laurel

This hold even though those are adjusted percentages?

-----Original Message-----
From: Copeland, Laurel
Sent: Friday, September 19, 2003 11:26 AM
To: Eby, Elizabeth
Cc: VHAANN HSRD Statistical Group

The raw odds ratio can be calculated...17% of 334=277, 20% of 2741=2193
cut back?
no  yes
priv no   277  57
ins? yes 2193 548

OR = (277/57) / (2193/548)
=  4.86  /  4.00
= approx 1.22
The remainder of the effect in the adjusted OR must be due to the
covariates.

-----Original Message-----
From: Eby, Elizabeth
Sent: Friday, September 19, 2003 11:05 AM
To: VHAANN HSRD Statistical Group

How would you explain the small difference in the adjusted percentages (17%
vs 20%) with an odds ratio of 1.7 (p=.04)?  Does it have anything to do with
the underlying sample sizes of the 2 groups (n=334 VA patients and n=2741
with private insurance)?

Thanks.

-----Original Message-----
From: jpiette@umich.edu [mailto:jpiette@umich.edu]
Sent: Friday, September 19, 2003 10:51 AM
To: elizabeth.eby@med.va.gov
Subject:

Liz - can you double check this?  THe difference in %'s seem small relative
to
the AOR.

Controlling for their sociodemographic characteristics, number of chronic
diseases, and number of prescription medications, 17% of VA patients cut
back
on medication use due to cost compared to 20 % of those with private
insurance
(adjusted odds ratio [AOR]: 1.7, p=.04),
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