APH 1997, 55, 169-178:

Reliability of a questionnaire designed to measure smoking intervention among secondary school students.

M. Csincsak, L. Maes, D. De Bacquer, and G. De Backer

Keywords: smoking prevention, adolescents, reliability, Belgium

Objectives.  In the framework of the evaluation of a smoking prevention program for youngsters, a reliability study of the questionnaire was conducted.  The questionnaire was designed to measure attitudes, self-efficacy, perceived social norms, social skills, short-term and long-term intentions to smoke, knowledge of smoking restrictions at school, communication with smokers and non-smokers and smoking behaviour of the respondents as well of their parents, siblings and friends.

Methods.  A total of 753 students were eligible for a test-retest evaluation of the questionnaire with a 2-weeks interval.  Out of these 753 pupils, 656 (87%) had duplicate questionnaires, reasons for drop-out mainly being absence and incorrect identification data resulting in problems of individual matching.  Test-retest agreement of the data was statistically evaluated according to intra-class correlation coefficients (ICC) and kappa statistics.

Results.  The ICC coefficients for attitude, self-efficacy and communication with the smokers and non-smokers were between 0.57 and 0.80.  However, the mean score at the retest for self-efficacy and communication with smokers of the students as a group, showed a highly significant systematic increase compared to the first test.  Highest kappa statistics (>0.90) were found for smoking behaviour of the parents, while lowest values were observed for each of the 3 perceived social norms items (0.50) and to a lesser extent for intention to smoke within the forthcoming month.

Conclusions.  These results indicate that questions to assess smoking behaviour of youngsters and possible determinants in the framework of an evaluation study can have heterogenous reliability values.  Care should be taken in the interpretation of specified information related to items as perception of smoking prevalence rates, intention to smoke in the future and beliefs about own capabilities of quitting or no smoking in specific situations.