Reliability of a dietary questionnaire on food habits, eating behaviour and nutritional knowledge of adolescents.

Objective: To develop a dietary questionnaire on food habits, eating behaviour and nutrition knowledge of adolescents and to examine its reliability. Design: A cross-sectional baseline survey. The questionnaire was self-administered to study participants twice with 7 days between each administration. Setting: A school community in Pavia, Italy. Subjects: A group of students (n¼72, aged 14–17 y, both sexes) studying in a secondary school in the second year of the course were invited to compile a dietary questionnaire during school time. Informed written consent was obtained from each subject and their parents. Subjects were initially recruited for a nutrition intervention; recruitment was opportunistic and school based. Statistical analyses: Reliability was assessed using the Cronbach’s alpha and the Pearson correlation coefficients. Results: Cronbach’s alpha ranges from a minimum of 0.55 to a maximum of 0.75, indicating that only two sections have a poor internal consistency. The Pearson correlation coefficients range from a minimum of 0.78 to a maximum of 0.88, indicating a very good temporal stability of the questionnaire. All the Pearson correlation coefficients are statistically significant with Po0.01. Conclusions: The present questionnaire has the potential to measure the effects of nutrition interventions on adolescents because of its stability in making comparisons over time. The instruments is low in cost and easy to administer and analyse; moreover, it could be modified appropriately to fit the needs of other populations as well.