5 Farm Accidents Survey 2004: Venn diagramme Frame population * Target population * Sample Measurement study * Nonresponse study Overcoverage
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 Measurement study by subsampling Retrospective questions Subsample among farms without accidents Survey and adjust! Two-phase estimation
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 Conclusions Regard all sources of errors! Retrospective survey risk of measurement bias! Evaluate more surveys!