Cluster randomised controlled trial of expert system based on the transtheoretical (“stages of change”) model for smoking prevention and cessation in schools

Pupils started the computer programme with their identification number and password, so on second and third sessions feedback could be given on their progress. We therefore had an accurate attendance register and calculated percentage attendance for each occasion of use. Pupils could skip through the programme by pressing the continue button, which would mean that although they attended physically, they missed the individualised messages. The computer programme, however, measured the time taken to complete the interventions. To assess how long was necessary to get the messages, we asked four "smokers" in our department and four "non-smokers" to use the intervention rapidly but attentively. We calculated the mean time necessary (7 minutes for a non-smoker and 11 minutes for a smoker) and hence the percentage of smokers and non-smokers who took long enough to have received the full intervention. At the end of the computer programme, a five item Likert scale questionnaire recorded students’ reactions to the programme each time they used it. We calculated the percentage of smoking and non-smoking participants who endorsed either of the two positive responses by occasion of use.