Koordeman et al. (2011) conducted a study on the effect of alcohol commercials on alcohol consumption in a movie theater. Participants saw one of two types of beverage commercials: alcoholic or nonalcoholic. Their consumption of alcohol during the movie was then measured. Finally, they completed a questionnaire on their usual drinking habits. Koordeman et al. found that young adults who generally consume large amounts of alcohol each week were influenced to drink more alcohol when they saw alcohol commercials, whereas the alcohol consumption of young adults who generally consume small amounts of alcohol each week was not influenced by the type of commercial shown. What type of design is this?