1. Using weighted data on the HSE Susan Purdon Survey Methods Unit, NatCen

2. Sample design Core sample: equal probability of selection for adults; non-equal for children Boost sample: non-equal probabilities of selection To date: core adult sample unweighted; children weighted; boost samples weighted

3. The case for using non-response weights

4. Reasons for weighting for non-response Estimates for all adults are currently biased towards elderly/women. Weighting would correct this. Most large-scale government sponsored surveys now use weights

5. Reasons for not weighting for non-response Most analysis done within age/sex groups and not much evidence of bias within these Three sets of weights needed: interview, nurse, blood Weights complicate the analysis Time series problems

6. Proposed strategy Each year weight HSE so that core sample has correct age/sex distn by region Will give three sets of weights: interview; nurse; blood Check against census for any other major biases Check that each sub-sample has similar health and health behaviour characteristics First year=2003; retrospective? (all, or one cross-over year?)

7. Expected changes to estimates (1)

8. Expected changes to estimates (2)