1. 1 Measurement Bias Adjustment in the Swedish Farm Accidents Survey Jörgen Svensson, Statistics Sweden

2. 2 To look between the street-lamps! Under the lamps: standard errors Between the lamps: nonresponse bias, measurement bias etc.

3. 3 Farm Accidents Survey 2004: main study Target population: Swedish farms Frame: Swedish Farm Register 2003, with 67 000 farms Sample size: 7000 farms Sampling design: stratified Pareto πps Data collection: postal questionnaire + telephone interviewing

4. 4 Farm Accidents Survey 2004: follow-up studies Measurement study: telephone interviews with 400 farms Nonresponse study: telephone interviews with 400 farms

5. 5 Farm Accidents Survey 2004: Venn diagramme Frame population * Target population * Sample Measurement study * Nonresponse study Overcoverage

6. 6 Hansen-Hurwitz plan (subsampling of nonrespondents) Nonresponse follow-up and adjustment Simple random sampling within strata for nonrespondents Presupposes very high response rate for the subsample Two-phase estimation

7. 7 Measurement study by subsampling Retrospective questions Subsample among farms without accidents Survey and adjust! Two-phase estimation

8. 8 The result of the survey Measurement study 4 7 per cent of the farms had accident(s) Nonresponse study marginal adjustment Few accidents are reported to the social insurance office

9. 9 Conclusions Regard all sources of errors! Retrospective survey risk of measurement bias! Evaluate more surveys!