A forensic psychologist was interested in the possible effects of several variables on the ability of witnesses to recall information about a crime. Participants viewed one of four 10-minute video clips depicting a crime event. In the video clips, the investigator manipulated the race of the crime perpetrator (same or different from that of the participant) and the type of crime that was committed (violent or nonviolent). After viewing a single video clip, each participant answered a series of questions about the event depicted in the video. The number of questions answered correctly determined the recall score for that participant. What type of design is this study