A personality psychologist was interested in examining whether the prevalence of narcissism differed between people based on the type of pet they own: cats, dogs, or exotic pets. She administered a questionnaire that probed narcissistic personality traits to randomly selected participants. She collapsed the questionnaire items into a continuous- valued composite index of narcissism prevalence. She included biological sex as a factor in her analysis to examine whether biological sex interacts with pet type to influence the prevalence of narcissism. This gave her a 23 experimental design with sex (men, women) and pet type (cat, dog, exotic) as factors.