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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