Reliability and validity of television food advertising questionnaire in Malaysia

Interventions to counter the influence of television food advertising amongst children are important. Thus, reliable and valid instrument to assess its effect is needed. The objective of this study was to determine the reliability and validity of such a questionnaire. The questionnaire was administered twice on 32 primary schoolchildren aged 10-11 years in Selangor, Malaysia. The interval between the first and second administration was 2 weeks. Test-retest method was used to examine the reliability of the questionnaire. Intra-rater reliability was determined by kappa coefficient and internal consistency by Cronbach's alpha coefficient. Construct validity was evaluated using factor analysis. The test-retest correlation showed moderate-to-high reliability for all scores (r = 0.40*, p = 0.02 to r = 0.95**, p = 0.00), with one exception, consumption of fast foods (r = 0.24, p = 0.20). Kappa coefficient showed acceptable-to-strong intra-rater reliability (K = 0.40-0.92), except for two items under knowledge on television food advertising (K = 0.26 and K = 0.21) and one item under preference for healthier foods (K = 0.33). Cronbach's alpha coefficient indicated acceptable internal consistency for all scores (0.45-0.60). After deleting two items under Consumption of Commonly Advertised Food, the items showed moderate-to-high loading (0.52, 0.84, 0.42 and 0.42) with the Scree plot showing that there was only one factor. The Kaiser-Meyer-Olkin was 0.60, showing that the sample was adequate for factor analysis. The questionnaire on television food advertising is reliable and valid to assess the effect of media literacy education on television food advertising on schoolchildren.