Childhood participation in sports, cultural groups, and youth groups appears to be related to enhanced self-esteem for adolescents (McGee, Williams, Howden-Chapman, Martin, & Kawachi, 2006). In representative study, a sample of n=100 adolescents with history of group participation is given a standardized self-esteem questionnaire. What measurement system (e.g., nominal, ordinal, interval, ratio) would be used to test the dependent variable, and why?