Re: which test for trend?

Posted by Bruce Weaver on Jan 17, 2011; 9:38pm
URL: http://spssx-discussion.165.s1.nabble.com/which-test-for-trend-tp3341921p3345177.html

The data shown below were for one particular organism-antibiotic combination.  So I think organism, antibiotic, and organism*antibiotic are other terms to include in the model.  Various interactions involving Year may be of interest too.  

HTH.

Gene Maguin wrote

Aline,

Ok, so you have 8000+ records over 7 years. Each record is 'yes/no' with
respect to resistance. It also sounds like each of the 8000 records probably
is a separate individual. Perhaps not completely but you certainly haven't
got 7 years of samples for 1000+ persons. My suggestion is to use logistic
regression. Sounds like Year (0-6) is your only IV. You could treat year as
continuous or categorical. Logistic is correct for a categorical DV.

Gene Maguin



-----Original Message-----
From: SPSSX(r) Discussion [mailto:[e-mail]] On Behalf Of
AB365
Sent: Monday, January 17, 2011 3:43 PM
To: [e-mail]
Subject: Re: which test for trend?

Thanks for your reply, I really appreciate it. Sorry I wasn't clear enough.
The data I have are repeated period prevalence studies. So for the month of
Feb each year I have resistance data on every urine sample which tested
positive for bacterial species in a geographic region (first positive sample
per patient as far as I could identify). This data is surveillance data, so
probably not up to research standards, however I do have data on 8000+
samples in total and this data is not something that is available for this
area in published literature. That is why I am interested in trends, because
hopefully whatever errors there are are stable over the time period, so even
if the resistance rates aren't exactly accurate the trends should show which
way things are heading. I don't have the exact data in front of me but it
would look something like this for a particular organism-antibiotic
combination:

Feb 2004 S=250 R=250 (50%R)
Feb 2005 S=300 R=270 (47%R)
Feb 2006 S=270 R=250 (48%R)
Feb 2007 S=250 R=300 (54%R)
Feb 2008 S=210 R=230 (52%R)
Feb 2009 S=285 R=300 (51%R)
Feb 2010 S=230 R=250 (52%R)

Thanks for your help
Aline
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