Development of a reliable and valid nutritional knowledge questionnaire for urban South African adolescents

Abstract

Objectives We wanted to develop a valid and reliable nutritional knowledge test for urban South African adolescents who were participating in the Birth-to-Twenty cohort study. The questionnaire was intended for use every second year, from ages 13 to 14 y until age 20 y. Methods Theinitial steps involved the development of a conceptual framework andidentification of nutritional concepts in collaboration withnutritional experts, and this defined the construct of thequestionnaire. The South African national teaching curriculumobjectives for nutritional education and other relevant issues wereselected as the desired concepts, and most items were phrased inaccordance with the recently developed South African Food-Based DietaryGuidelines. Thereafter, 140 items (questions) were developed and inturn assessed by an expert panel, and the result was that only 88 itemsremained. This was done to ensure content and face validity of theitems. The 88 items were constructed into a questionnaire and pilotedfor appropriateness and understanding by adolescents, ages 13 to14 y, as a means of assessing face validity by non-experts.The edited preliminary questionnaire (still with 88 items) wasadministered to a nutrition expert group ( n= 71) versus a non-expert group ( n= 82), referred to as sample 1, for the purposes of performingitem analysis and assessing construct validity of the questionnaire.The result of the analysis, a 63-item questionnaire, was administeredto adolescents at three school grade levels, 8( n = 128), 10 ( n= 143), and 12 ( n = 98),referred to as sample 2, which was representative of the grades inwhich the Birth-to-Twenty group will be in when the questionnaire isadministered. The questionnaire was administered to the sample toassess its content validity and internal consistency reliability. Thefinal questionnaire had 60 items, and its construct, content, andinternal consistency reliability werereassessed. Results Thefinal 60-item questionnaire displayed a significant difference( P < 0.0001) in the mean scores of the expertand non-expert groups tested. It had internal consistencies(Cronbach's α) of 0.71, 0.79, and 0.82 for grades 8, 10,and 12 respectively, and an overall value of 0.77 for all groupscombined. However, it was less than 0.7 for most grade 8 pupils and forall grades at a historically disadvantagedschool. Conclusion Anutritional knowledge questionnaire with construct, face, and contentvalidities and internal consistency was developed for use in SouthAfrican adolescents to evaluate their nutritional knowledge. Internalconsistency was low in children at a disadvantaged school and those ingrade 8 compared with multiracial groups at a multiracial school. It isrecommended that pupils at disadvantaged schools be assisted by trainedinterviewers when taking thetest.