The development of a valid and reliable nutrition knowledge questionnaire and performance-rating scale for urban South African adolescents participating in the 'Birth-to-Twenty' study

Thesis (MSc)--University of Stellenbosch, 2005.ENGLISH ABSTRACT: The Birth to Twenty (BTT) study involves the monitoring of the health status and related factors of urban-born children from birth until age twenty. When the cohort reached age 13 years in 2003, nutrition knowledge assessment was identified as an important new priority and a nutrition knowledge questionnaire was required for these purposes. Subsequently a valid and reliable nutrition knowledge questionnaire was developed for the BTT study. This process started with the development of a conceptual framework of nutrition-related issues facing urban South African adolescents and identification of related nutrition concepts. A pool of potential questionnaire items reflecting the concepts was subsequently developed. These items were evaluated by an expert panel to ensure content and face validity before being structured into a questionnaire. The resulting 88-item questionnaire was completed by adult and adolescent samples, each age group comprising subgroups of those likely to have good nutrition knowledge and those likely to have poor nutrition knowledge. The data obtained from the completion of the questionnaire by these groups was used to refine the questionnaire through the determination of difficulty and discriminatory indices of the items, and the deletion of items that did not meet the stated criteria. The construct validity of the remaining 63 items was assessed using the same data set. To assess the internal consistency reliability (ICR) of the 63-item questionnaire it was completed by an adolescent sample population considered to be representative of the BTT cohort, after which the questionnaire underwent further steps of refinement. The result was a 60-item questionnaire of which the ICR and construct validity was reassessed and found to be satisfactory. However, to ensure the accurate interpretation of scores obtained by testees, the development of a performance-rating scale was necessary. A norm-referenced performance-rating scale (norms) was developed by administering the nutrition knowledge questionnaire to a sample population similar to the BTT cohort (norm group) and transforming their performance scores to z-scores. The z-scores ranges were then categorised into stanines, thereby resulting in a norm-referenced performance-rating scale that can be used to rate the performance of the BTT cohort. The validity of the norms was assessed by administering the nutrition knowledge questionnaire to three validation groups that comprised groups who were expected to obtain different performance-ratings on the questionnaire based on their varying levels of nutrition knowledge. The validation groups performed as expected, with significant differences in performance-rating profiles found among the three groups, indicating the validity of the norms. The study was successful in developing a reliable and valid nutrition knowledge questionnaire for use on the urban adolescents who participate in the BTT study. A norm-referenced performance-rating scale for use with the questionnaire was also successfully developed. The questionnaire and norms will be useful in assessing nutrition knowledge as well as in comparing the changes in knowledge of the BTT cohort as they move from lower to higher school grades.AFRIKAANSE OPSOMMING: Die “Birth to Twenty” (BTT)-studie behels die monitering van die gesondheidstatus en verwante faktore van kinders wat in stedelike gebiede gebore is van geboorte tot twintigjarige ouderdom. Toe die kohort in 2003 dertienjarige ouderdom bereik het, is die evaluering van die voedingkennis van die kinders as ‘n belangrike nuwe prioriteit geïdentifiseer. ‘n Toepaslike voedingkennisvraelys is vir hierdie doeleindes benodig en gevolglik is ‘n geldige en betroubare vraelys vir gebruik in die BTT-studie ontwikkel. Hierdie proses is begin deur die ontwikkeling van ‘n konseptueleraamwerk oor voedingverwante vraagstukke wat stedelike Suid-Afrikaanse adolessente in die gesig staar, asook die identifisering van verwante voedingkonsepte. ‘n Poel van potensiële vraelysitems wat die konsepte reflekteer is daarna ontwikkel. Die items is eers deur ‘n paneel van kenners evalueer om inhoud- en gesigsgeldigheid te verseker alvorens dit in ‘n vraelys omskep is. Die produk was ‘n vraelys wat 88 items ingesluit het wat vervolgens deur volwasse en adolessente groepe voltooi is. Die groepe het subgroepe ingesluit van diegene met verwagte goeie voedingkennis en diegene met verwagte swak voedingkennis. Die data wat tydens hierdie stap gegenereer is, is gebruik om die vraelys verder te verfyn deur die bepaling van die moeilikheids- en diskriminatoriese-indekse van die items. Die items wat nie aan vooraf gestelde kriteria voldoen het nie, is weggelaat. Die konstrukgeldigheid van die oorblywende 63 items is bepaal deur dieselfde datastel te gebruik. Om die interne-konsekwensie-betroubaarheid (IKB) van die vraelys te bepaal, is dit deur ‘n steekproef van adolessente, wat verteenwoordigend van die BTT-kohort is, voltooi. Hierna is die vraelys verder verfyn. Die uitkoms was ‘n 60-item vraelys waarvan die IBR en konstrukgeldigheid weereens bepaal is. Dit is gevind dat dié twee indikatore van geldigheid en betroubaarheid bevredigend is. Om akkurate interpretasie van die punt wat deur ‘n respondent vir die toets behaal te verseker, is die ideal om ‘n skaal te ontwikkel wat gebruik kan word om dié punt te takseer. ‘n Norm-gebaseerde prestasietakseringskaal is ontwikkel deur die voedingkennisvraelys deur ‘n steekproef wat verteenwoordigend is van die BTT-kohort (normgroep), te laat voltooi. Die prestasiepunte is getransformer na z-tellings wat vervolgens getransformeer is na stanneges, wat ‘n norm-gebaseerde prestasietakseringskaal opgelewer het wat gebruik kan word om die prestasie van die BTT-kohort te takseer. Valideringsgroepe met verskillende vlakke van voedingkennis, wat dus na verwagting verskillend getakseer behoort te word indien die norme toegepas word, het die voedingkennisvraelys voltooi om die geldigheid van die norme te bepaal. Dié valideringsgroepe het soos voorspel presteer, met betekenisvolle verskille in die prestasieprofiele van die verskillende groepe. Hierdie resultate dui daarop dat die norme geldig is. Die ontwikkeling van ‘n geldige en betroubare voedingkennistoets vir gebruik in die BTT-studie is suksesvol in hierdie studie deurgevoer. ‘n Norm-gebaseerde prestasietakseringskaal vir gebruik saam met die vraelys is ook suksesvol ontwikkel. Die vraelys en norme sal van waarde wees vir die evaluering van die voedingkennis van die BTT-kohort. Dit sal ook met sukses gebruik kan word om die verandering in die voedingkennis van die kinders soos wat hulle ouer word, te bepaal

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

A nutritional knowledge questionnaire with construct, face and content validities and internal consistency was developed for use in South African adolescents to evaluate their nutritional knowledge. Internal consistency was low in children at a disadvantaged school and those in grade 8 compared with multiracial groups at a multiracial school. It is recommended that pupils at disadvantaged schools be assisted by trained interviewers when taking the test

Development of a valid and reliable nutrition knowledge questionnaire for urban adolescents

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The development and testing of 2-dimensional drawings and 3-dimensional food models to estimate food portion size in 12-13 year old children in the birth-to-twenty cohort in Johannesburg

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