You are asked to help consult on a study which was recently completed in coastal African country. In this study, a total of 274 soldiers stationed in three different camps were examined and tested for the presence of bacterial sexually transmitted diseases (STD) and human immunodeficiency virus (HIV) positivity. In addition to the information from the clinical exam and laboratory specimens, interviews were conducted to gather information on age, years of military service, ethnicity, and region of origin. The data are now to be analyzed to learn which factors were associated with the presence of STDs, including HIV. What is the most accurate description of this study design?