Posted by
Charlotte-9 on
Aug 29, 2006; 3:55pm
URL: http://spssx-discussion.165.s1.nabble.com/Compare-odds-ratios-tp1070604p1070607.html
Hi Marta,
Thanks for your response. I think it's fair to say that I'm having a bad
day (month, actually) and my brain packed up for a while there. I
realised as soon as I posted the question that it was stupid! I
understand everything you have said below, so feel happy at interpreting
the results. I think I'm going to have to adopt a policy of not looking
at this other report because it sends me insane!!
Thanks to you and everyone else who responded for your help.
Lou
On Tue, 29 Aug 2006 16:50:27 +0200, =?ISO-8859-1?B?
TWFydGEgR2FyY+1hLUdyYW5lcm8=?= <
[hidden email]> wrote:
>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)