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help for ^effmod ^                                               (STB-36: sbe14)
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ORs and CIs for Logistic Models with Interaction
------------------------------------------------

    ^effmod^ dvar  evar  [^if^ exp]^,^ [^cov^ariate^(^cov_list^)
        int^eract^(^interaction #^) ed^iff^(^#^) mod^el ^l^evel^(^#^)^]


Description
-----------

^effmod^ calculates user specified stratum specific odds ratios and confidence
 intervals for logistic regression models which include interaction terms
 between an exposure and effect modifiers. If the model has been specified
 previously or ^effmod^ is repeated with new stratum values, the current model
 estimates are used; otherwise a new model is fit.
  
 
Variables and options required
------------------------------

    dvar is the "disease" variable  (dichotomous outcome)
    
    evar is the "exposure" variable  (dichotomous, ordinal, or interval)

    ^covariate(^cov_list^)^ is the list of confounders in model
    
    ^interact(^interaction #^)^ is the  list of interaction variables in model 
        plus a stratum value for each effect modifier; for more than one 
        interaction term, the form is: 
        ^interact^(interaction1 # interaction2 # ...^)^.


Options allowed 
---------------

    ^ediff(^#^)^ is the difference of values for exposed versus unexposed.
        For example, to compare age=50 versus age=40, ^ediff^ would be 
        specified as ^ediff(10)^. The default for ^ediff^ is 1, which is 
        equivalent to exposed=1 versus unexposede=0.

    ^level(^#^)^ specifies the confidence level in percent for the
         confidence intervals.  The default is a 95% confidence interval.
      
    ^model^ displays the logistic regression table.


Examples
--------

 . ^effmod chd cat, cov(smk ecg chl) int(catxchl 300) model^

     Calculates the odds ratio and 95% confidence interval for the association
     between coronary heart disease (chd: 1=yes, 0=no) and catecholamine
     (cat: 1=high, 0=normal) among individuals with a cholesterol level (chl)
     of 300; displays model

 . ^effmod chd cat, cov(smk ecg chl) int(catxchl 250 catxecg 1) level(90)^
 
     Odds ratio and 90% confidence interval for the association between chd
     and cat among individuals with chl=250 and an abnormal ecg (ecg=1)
 
 . ^effmod chd sbp, cov(smk ecg chl) int(sbpxsmk 1) ediff(20)^

     Odds ratio and 95% confidence interval for the association between chd and
     a 20mmHg difference in systolic blood pressure (sbp) among smokers (smk=1)


Author
------

     Joanne M. Garrett
     University of North Carolina
     garrettj@@med.unc.edu


Also see
--------

    STB:  STB-36 sbe14
On-line:  @effmod@ (if installed)