odds ratios after logistic regression

[Ann Fitzmaurice]

hi

i run the following model , logistic regression dependent vara varb varc
vara*varb

what i need to do now is to calcuate the odds ratios to complete a table a
by b, where a has 4 levels and b has 3 levels including confidence
intervals

does anyone  know how to do this , and if so do they have an example

thanks
ann

=====================
To manage your subscription to SPSSX-L, send a message to
[hidden email] (not to SPSSX-L), with no body text except the
command. To leave the list, send the command
SIGNOFF SPSSX-L
For a list of commands to manage subscriptions, send the command
INFO REFCARD

[Bruce Weaver]

Hi Ann.  I suggest you use GENLIN (with DISTRIBUTION=BINOMIAL LINK=LOGIT) rather than LOGISTIC REGRESSION, as it has the EMMEANS sub-command that will give you the kind of table you describe.  Here's an example I worked out a while ago for a 2x2 situation, but it should be straightforward adapting it to your model.  As you can see, I used OMS to send the Pairwise Comparison results to another dataset so that I could process them further.


* OMS.
DATASET DECLARE  PairWise.
OMS
  /SELECT TABLES
  /IF COMMANDS=['Generalized Linear Models'] SUBTYPES=['Pairwise Comparisons']
  /DESTINATION FORMAT=SAV NUMBERED=TableNumber_
   OUTFILE='PairWise'.


GENLIN HSgrad (REFERENCE=FIRST) BY male white (ORDER=DESCENDING)
  /MODEL male white male*white INTERCEPT=YES
 DISTRIBUTION=BINOMIAL LINK=LOGIT
  /EMMEANS TABLES=male SCALE=TRANSFORMED
  /EMMEANS TABLES=white SCALE=TRANSFORMED
  /EMMEANS TABLES=male*white SCALE=TRANSFORMED compare=white
  /EMMEANS TABLES=male*white SCALE=TRANSFORMED compare=male
  /MISSING CLASSMISSING=EXCLUDE
  /PRINT CPS DESCRIPTIVES MODELINFO FIT SUMMARY SOLUTION (EXPONENTIATED).

OMSEND.
dataset activate PairWise window = front.

* Mean difference is on the log-scale, so exponentiate it to get an odds ratio.
compute OddsRatio = exp(MeanDifferenceIJ).
compute LowerLimit = exp(lower).
compute UpperLimit = exp(upper).
format OddsRatio to UpperLimit (f5.3).
list var1 to Std.Error  Sig to UpperLimit.

* MeanDifferenceIJ = fitted value for VAR2 minus
* fitted value for VAR3, within VAR1.
* E.g., for row 1, MeanDifferenceIJ = White - Other
* difference within MALES; on row 2, MeanDifferenceIJ =
* Other - White difference within MALES .
* So on row 1, the odds ratio is for White relative to Other;
* whereas on row 2, it is for Other relative to White, both
* within MALES only.  I.e., rows 1 and 2 give the simple
* main effects of White v Other, and Other v White.

If you want the full syntax file, drop me a line off-list (to the Lakehead U address in my signature file), and I'll send it to you.

HTH.
Bruce

Ann Fitzmaurice wrote

hi

i run the following model , logistic regression dependent vara varb varc
vara*varb

what i need to do now is to calcuate the odds ratios to complete a table a
by b, where a has 4 levels and b has 3 levels including confidence
intervals

does anyone  know how to do this , and if so do they have an example

thanks
ann

=====================
To manage your subscription to SPSSX-L, send a message to
[hidden email] (not to SPSSX-L), with no body text except the
command. To leave the list, send the command
SIGNOFF SPSSX-L
For a list of commands to manage subscriptions, send the command
INFO REFCARD