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help for ^epiconf^ 
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Assessing confounding effects in epidemiological studies 
---------------------------------------------------------------

    ^epiconf^ yvar xvar,  [^con^(covlist) ^cat^(covlist) ^m^odel(string)
		^nog^raph ^b^ackward  ^e^xpos(varname) ^d^ead(varname) ^det^ail 
		^l^evel(#) ^co^ef graph_options]
        
^epiconf^ calculates the change in effect estimates such as odds ratio, 
rate ratio, or hazard ratio after adjusting for a potential confounder 
using either "forward selection" or "backward deletion" strategies. 

^epiconf^ also calculates and graphs adjusted effect measures and 
their confidence intervals. The order of variables being selected is 
based on the "importance" (magnitude) of "change in estimate". 
  
Variables required
------------------

    ^yvar^ -- dependent variable, binary variable for logistic or poisson 
        regression; survival time variable for Cox proportional hazards
        model.  

    ^xvar^ -- exposure of interest
         
Options 
-------
    ^con^ -- list of potential continuous confounding variables. 
    ^cat^ -- list of potential categorical confouding variables. 
    ^m^odel^(^string^)^ -- specifies the regression method, default is 
        logistic regression (^logit^), ^poisson^ and ^cox^ can be 
        specified. 

    ^nog^graph -- suppresses graphs. By default, a graph is given.   

    ^b^ackward -- specifies selection strategy as "back deletion method", 
        otherwise, "forward selection" method is default.

    ^e^xpos(varname) -- specifies a variable that reflects the amount of 
        exposure over which the ^yvar^ events were observed for each 
        observation. This is the option only for ^poisson^ regression.      

    ^d^ead(varname) -- specifies the name of a variable recording 0 if 
        censored and nonzero -- typically 1 -- if failure. If dead() is 
        not specified, all observations are assumed to have failed.  This
        is the option only for ^cox^ regression.

    ^co^ef -- graphs regression coefficients instead of effect estimates 
        for graphs.

    ^det^ail -- gives details at each step. Default only gives a summary. 

    ^l^evel(#) -- specifies the confidence level, in percent, for 
        calculation of confidence intervals (default=95%)      

    ^graph_options^ -- some options with ^graph^ are allowed; see help 
        @graph@.


Examples
--------

 .  ^epiconf dead ab_uria, con(sbp weight) cat(sex agegroup)^
        Calculates and graphs crude and adjusted odds ratios using
        logistic regressions with a forward selection approach. 
        
 .  ^epiconf dead ab_uria, con(weight sbp) cat(sex agegroup) m(poisson)^ 
 	^e(time) detail^
        Calculates and graphs crude and adjusted rate ratios using poisson
        regressions with a backward deletion method. Details in each step 
        are given.

 .  ^epiconf time ab_uria, con(age weight) cat(sex) m(cox) dead(dead) nograph^
        Calculates crude and adjusted hazard ratio using Cox proportional 
        hazard models a backward deletion method, suppressing graph.

Author
------
    Zhiqiang Wang
    Menzies School of Health Research, Darwin, Australia
    wang@@menzies.su.edu.au
