The impact of complex survey design on prevalence estimates of intakes of food groups in the Australian National Children’s Nutrition and Physical Activity Survey

Objective: To assess the impact of the complex survey design used in the 2007 Australian National Children’s Nutrition and Physical Activity Survey (ANCNPAS) on prevalence estimates for intakes of groups of foods in the population of children. Design: The impacts on prevalence estimates were determined by calculating design effects for values for food group consumption. The implications of ignoring elements of the sample design including stratification, clustering and weighting were discussed. Setting: The 2007 ANCNPAS used a complex sample design involving stratification, a high degree of clustering and estimation weights. Subjects: Australian children aged 2-16 years. Results: Design effects ranging fromignored, prevalence estimates were also biased. Conclusions: Ignoring complex survey design used in the ANCNPAS could result in underestimating the width of confidence intervals, higher mean square errors and biased estimators. The magnitude of these effects depends on both the parameter under consideration and the chosen estimator.