Data Analysis
Data were analyzed with SPSS version 10.0. The statistical tests used in the data analysis included descriptive statistics, the Phi, contingency, and point biserial correlations, and logistical regression analyses. Descriptive statistics were reported for the demographic variables(gender, race, grade, and disposable income), and smoking behavior (frequency, age of initiation, ability to quit, and quit attempts), perceived availability (1=very difficult and 7=not at all difficult), and sources (commercial or social) of tobacco. Correlations were also reported. The dependent variable was adolescent provision of tobacco to other adolescents in the past month. The independent variables were demographics, social influences (friend or family), perceived sanctions (high, medium, low), perceived availability, source of most recent cigarettes (commercial or social), age of initiation, purchase attempts, number of weekly cigarettes, and ownership of tobacco merchandise. School sanctions were defined as low (nothing to sent to the office), medium (stay after school to required to attend special class), and high (suspended from activities to expelled).
A logistic regression analysis was used to identify potential predictor variables of adolescent provision of tobacco to other adolescents using SAS 8.0. The independent variables were demographics, social influences, perceived sanctions, perceived availability, sources of cigarettes, smoking behavior, and ownership of tobacco brand items. The dependent variable was adolescent provision of tobacco to other adolescents in the last 30 days. Variables were included in the final logistic regression model by forward stepwise selection. The likelihood-ratio(LR) test was used to determine removal of variables from the model at each step. Entry of variables at each step based on .25 and the significance criterion for selection of whether a variable remained in the model was .05 (Allison, 1999). Nagelkerke’s Max-rescaled R2 was used to estimate the variation in the outcome variable explained by the logistic regression model (Nagelkerke, 1991; Norusis, 1999).
Results
Sources of Tobacco
Smokers perceived that it was easy to get cigarettes from friends, vending machines, and over-the-counter purchases. It was difficult to get cigarettes from family members (M = 3.4) and by stealing (M = 3.0) them from a store. Weekly smokers reported that it was not difficult to get cigarettes from friends (M = 6.2), vending machines (M = 5.5), and through over-the-counter purchases (M = 5.2). Weekly smokers (M = 4.1) perceived that it was easier to get cigarettes from family members than ever smokers (M = 3.4). Friends accounted for the largest reported source of initial, most recent and ever source of cigarettes. Family accounted for the second largest initial and ever source. Store purchases accounted for the second most recent source. If family and friends are combined as an initial source of tobacco, approximately 93% of ever smokers obtained cigarettes from social sources, compared with 6% who obtained them from commercial sources. Less than 1% reported getting their most recent cigarettes by stealing them from a store. Students were certain in their ability to quit smoking (M=5.0, SD=2.2).