Paul R. Yarnold
Optimal Data Analysis, LLC
Samples of 1,171 male and 1,503 female Anglo-American, 291 male and 503 female Mexican-American, and 138 male and 361 female Indian-American, non-smoking college undergraduates were asked if their best boy-friend or their best girl-friend would be most upset if the subject began smoking. Original analysis using separate chi-square analyses (one design cell for the Indian-American students violated the minimum expectation assumption) concluded: “While the influence of boy-friends or girl-friends on their smoking or non-smoking partners seemed to be rather small, the opposite-sex friend was invariably perceived to be more upset by the possibility of the respondent’s taking up the habit: all these differences were significant beyond the .01 level”. An exploratory GenODA analysis was conducted treating ethnicity as the Gen variable: an ODA model is identified that, when simultaneously and independently applied to each of the Gen groups (dummy-coded as 1-3), explicitly maximizes the lowest ESS obtained across all of the Gen groups. Here the subject’s gender is the class variable, and the gender of one’s most-affected friend is a categorical attribute (gender variables were dummy-coded: female=0, male=1). The omnibus GenODA model was: if Friend=female, predict subject gender=male; otherwise predict subject gender=female: p<0.0001, strong ESS=77.7 (84.9% of actual female and 92.8% of actual male subjects were correctly classified). The GenODA model performed comparably for the Anglo-, Mexican-, and Indian-American samples: all p’s< 0.0001; strong ESS=77.3, 81.3, and 75.1, respectively.