Posted by
Marta García-Granero on
Aug 29, 2006; 3:50pm
URL: http://spssx-discussion.165.s1.nabble.com/Compare-odds-ratios-tp1070604p1070609.html
Hi Lou:
If you have used logistic regression, then the answer is right in the
output:
- Check the dummy coding table to find out which dummy variable of the
set reflects "Muslim group" (could be ethnicity(1), or ethnicity(2)...
depending on the order of the categories).
- Check the Wald test significance for that dummy variable: that's the
significance you are looking for (caveats: not very sensitive, but it
can't be helped). Alternatively, the same information can be deduced
from the 95%CI for exp(b), provided you've been farsighted enough to
ask for them (this reminds me I have to write to Kyle Weeks
concerning some ideas and suggestions for SPSS 16, and that's one of
them: 95%CI should be default output in most statistical methods).
If you get lost with this explanation (about locating dummies and Wald
test and so on), just send the logistic regression output (draft) and
I'll point the important results to you
The term "adjusted odds-ratio" the authors used in the report means
that they used multiple logistic regression to control for other
factors (age and deprivation in this case).
L> Okay, I'll try to clarify matters. As usual, I'm trying to immitate work
L> that has been done previously, so the whole thing may be inappropriate.
The old "imitation theorem": "if it's published, then it's correct" ;)
L> I have used logistic regression to obtain adjusted odds ratios. The
L> outcome is 'screened' or 'not screened' and the independent variables are
L> age, ethnicity and deprivation. I am focusing on the odds ratios for the
L> ethnicity variable. When I talk about reference group, I mean that the
L> odds ratios are all calculated with respect to one group. In other words,
L> I have five Asian categories (Hindu, Muslim, Sikh etc) and the odds of
L> undertaking screening are compared to the odds for the non-Asian group
L> (the reference group). I am trying to show that the odds of undertaking
L> screening are lower for the Asian groups when compared to the non-Asian
L> group.
L> In previous analysis, the people who produced the report have stated the
L> following, "the Muslim group demonstrated a significantly (p<0.05) lower
L> uptake with adjusted odds ratio 0.37 versus 1.0 for non-Asians". I'm
L> basically trying to work out what they did and assumed they somehow
L> compared the odds.
L> Hope this clarifies things a bit - any suggestions gratefully received.
L> Best wishes,
L> Lou
L> On Tue, 29 Aug 2006 16:24:52 +0200, =?ISO-8859-15?B?
L> TWFydGEgR2FyY+1hLUdyYW5lcm8=?= <
[hidden email]> wrote:
>>Hi Lou
>>
>>Perhaps you havent' explained yourself completely... or I see an error
>>in your question: you just can't compare and odds-ratio with an odd,
>>and an OR from a group with the one of its reference group. I think
>>I'm being confused by the use of the term "reference group". Are you
>>talking about one qualitative variable that has been dummy coded, with
>>one group being the reference or is it something different?
>>
>>L> Could someone please tell me the correct test to use to compare whether
>>L> two odds ratios are significantly different. For instance, I want to
>>L> compare the odds ratio for group A (odds ratio = 0.487) against the
L> odds
>>L> ratio for the reference group (odds = 1).
>>
>>
>>--
>>Regards,
>>Dr. Marta García-Granero,PhD mailto:
[hidden email]
>>Statistician
>>
>>---
>>"It is unwise to use a statistical procedure whose use one does
>>not understand. SPSS syntax guide cannot supply this knowledge, and it
>>is certainly no substitute for the basic understanding of statistics
>>and statistical thinking that is essential for the wise choice of
>>methods and the correct interpretation of their results".
>>
>>(Adapted from WinPepi manual - I'm sure Joe Abrahmson will not mind)
L> __________ Información de NOD32, revisión 1.1724 (20060824) __________
L> Este mensaje ha sido analizado con NOD32 antivirus system
L>
http://www.nod32.com--
Regards,
Dr. Marta García-Granero,PhD mailto:
[hidden email]
Statistician
---
"It is unwise to use a statistical procedure whose use one does
not understand. SPSS syntax guide cannot supply this knowledge, and it
is certainly no substitute for the basic understanding of statistics
and statistical thinking that is essential for the wise choice of
methods and the correct interpretation of their results".
(Adapted from WinPepi manual - I'm sure Joe Abrahmson will not mind)