Transcript Measurement Bias Adjustment in the Swedish Farm Accidents Survey Jörgen Svensson, Statistics Sweden ”To look between the street-lamps!” • Under the lamps: standard errors • Between the.

Measurement Bias
Adjustment
in the Swedish
Farm Accidents Survey
Jörgen Svensson, Statistics Sweden
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”To look between the street-lamps!”
• Under the lamps:
standard errors
• Between the lamps:
nonresponse bias, measurement
bias etc.
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Farm Accidents Survey 2004:
main study
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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
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Farm Accidents Survey 2004:
follow-up studies
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Measurement study:
telephone interviews with 400 farms
Nonresponse study:
telephone interviews with 400 farms
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Farm Accidents Survey 2004:
Venn diagramme
Frame population
Overcoverage
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Nonresponse study
Measurement study
Sample
Target population
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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
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Measurement study by subsampling
• Retrospective questions
• Subsample among farms
”without accidents”
• Survey and adjust!
• Two-phase estimation
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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
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Conclusions
• Regard all sources of errors!
• Retrospective survey →
risk of measurement bias!
• Evaluate more surveys!
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