This report describes the choice of the preliminary design for the New Zealand Health Survey, to be implemented from 2011. The survey will use computer assisted personal interviewing. The sample will be selected using a multi-stage area design. The selected sample size will be around 12,000 people per year. This is envisaged as sufficient to provide adequate precision for estimates of key prevalences for adults and children. The main objectives of the sample design are: • The design should support analysis of the survey by multiple users, which implies avoiding great variation in estimation weights. • Estimates for children and adults are required. • A range of prevalences are to be estimated. These include health behaviours and health conditions. • Estimates by ethnic group are required. Māori estimates are the most important of these and Pacifica and Asian estimates are also required. Estimates by ethnic group (Māori, Pacific and Asian) are a particular priority. A typical multi-stage area-based design would not give adequate sample in these groups. Ensuring adequate estimates from these subpopulations, while preserving precision at the national level, was the main focus of this sample design. Two main strategies will be used to increase the effective sample sizes for these populations: • A dual frame approach will be used. An area-based sample from NZ as a whole will be combined with a list-based sample of addresses on the Electoral Roll, to boost Māori sample size, subject to successful testing of this approach. • The area-based sample will be targeted towards the subpopulations of interest, by assigning higher probabilities of selection to meshblocks with higher concentrations of these groups. Sections 2 and 3 of this report describe the main elements of the area-based sample design and the list-based Electoral Roll sample design, respectively. Section 4 summarises sample sizes for the preliminary design. Section 5 outlines other issues which tenderers may need to consider. Appendix 1 details how the design settings in Sections 2 and 3 were derived, and Appendix 2 has more detailed tables on DHB sample sizes and standard errors for three of the design options that were considered.
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