A MICROCOMPUTER PROGRAM FOR MULTIPLE LOGISTIC REGRESSION BY UNCONDITIONAL AND CONDITIONAL MAXIMUM LIKELIHOOD METHODS1

Abstract

A frequent procedure in matched case-control studies is to report results from the multivarlate unmatched analyses if they do not differ substantially from the ones obtained after conditioning on the matching variables. Although conceptually simple, this rule requires that an extensive series of logistic regression models be evaluated by both the conditional and unconditional maximum likelihood methods. Most computer programs for logistic regression employ only one maximum likelihood method, which requires that the analyses be performed in separate steps. This paper describes a Pascal microcomputer (IBM PC) program that performs multiple logistic regression by both maximum likelihood estimation methods, which obviates the need for switching between programs to obtain relative risk estimates from both matched and unmatched analyses. The program calculates most standard statistics and allows factoring of categorical or continuous variables by two distinct methods of contrast A built-in, descriptive statistics option allows the user to inspect the distribution of cases and controls across categories of any given variable