BACKWARD_EXPOSURE       Performs deviance-based backwards variable
                        selection in logistic regression with an
                        exposure.
FORWARD_EXPOSURE        Performs deviance-based forwards variable
                        selection in logistic regression with an
                        exposure
LIKE                    Obtains likelihood
MCMC_LOGIT_KEEP         Obtains posterior samples from an MCMC
                        algorithm to perform variable selection.
STEPWISE_EXPOSURE       Performs deviance-based stepwise variable
                        selection in logistic regression with an
                        exposure
