Investigators are interested in the relationship between maternal depression and bacterial vaginosis (BV) prior to delivery. In order to assess the relationship, the researchers attended a prenatal clinic in New Orleans, Louisiana and invited women that attended the clinic to take part in a thorough questionnaire about their pregnancy status. Women had to be in at least the second term of their pregnancy. After the questionnaire, the women were required to undergo a bacterial culture examination to confirm their BV status. Data from the women was collected, and the mothers were categorized as exposed (depressed) or unexposed (not depressed) based on results from the questionnaire as well as diseased (BV ) or non-diseased (BV-) based on the results from the culture analysis. Which risk measurement do you think would be most appropriate to compare the groups