Public Health Nutrition

Monitoring and surveillance

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

Sandy Burdena1 c1, Yasmine Probsta2, David Steela1 and Linda Tapsella2

a1 Centre for Statistical and Survey Methodology, University of Wollongong, Northfields Avenue, Wollongong, New South Wales 2522, Australia

a2 Smart Foods Centre, University of Wollongong, Wollongong, Australia

Abstract

Objective To assess the impact of the complex survey design used in the 2007 Australian National Children's Nutrition and Physical Activity Survey (ANCNPAS07) 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 are discussed.

Setting The ANCNPAS07 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 from <1 to 5 were found for the values of mean consumption and proportion of the population consuming the food groups. When survey weights were ignored, prevalence estimates were also biased.

Conclusions Ignoring the complex survey design used in the ANCNPAS07 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.

(Received February 03 2011)

(Accepted November 09 2011)

(Online publication December 08 2011)

Correspondence

c1 Corresponding author: Email sburden@uow.edu.au

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