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Health Statistics & Informatics 1
WHO practices in imputation and estimation
Conference on Data Quality for International Organizations
Rome, Italy, 7-8 July 2008-05-28
Carla AbouZahrCoordinator, Statistics, Monitoring and Analysis
World Health OrganizationGeneva
Health Statistics & Informatics 2
Types of health statistics
• Unadjusted health statistics derived directly from primary data collection with no adjustments or corrections.
Health Statistics & Informatics 3
Health Statistics & Informatics 4
Types of health statistics
• Unadjusted health statistics derived directly from primary data collection with no adjustments or corrections.
• Adjusted health statistics corrected to deal with known biases, use of indirect techniques.
Health Statistics & Informatics 5
Health Statistics & Informatics 6
Types of health statistics
• Unadjusted health statistics derived directly from primary data collection with no adjustments or corrections.
• Adjusted health statistics corrected to deal with known biases, use of indirect techniques.
• Predicted health statistics based on a model relating the quantity of interest to covariates. – Forecasting: past relationships to predict future– Farcasting: missing primary data
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Health Statistics & Informatics 8
Source:Gareth JonesWHO/UNICEF database
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Source:Christopher MurrayInstitute for Health Metrics and Evaluation
Health Statistics & Informatics 10
Sources of data for global mortality estimates (circa 2004)
Complete VR Incomplete VR
Survey/census no data
Child mortality: q5 Adult mortality: 45q15
Source: WHO
Indirect methods problematic for adult mortality
Birth histories, Indirect methods;
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Health Statistics & Informatics 12
WHO principles for imputation
• Standard four-step procedure for estimation – a high-quality accessible database; – an independent peer review group; – published methods of estimation; margins of uncertainty– internal WHO clearance by HSI
• Country consultation– iterative process between Member States, WHO
country and regional offices and headquarters– feedback on quality of data collection and reporting;
strengthening country capacity to reproduce, produce and use estimates.
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External advisory bodies
• Disease-specific M&E reference groups– Include agencies and academic experts– Address coordination issues– Develop "best estimates": <5, maternal mortality,
coverage of interventions
• Advisory Committee on Health Monitoring and Statistics (ACHMS)– Independent outside experts – Gives inputs to WHO on its work, including Global
Burden of Disease, World Health Statistics.– Advises DG on scientific and technical issues.
Health Statistics & Informatics 14
Summary and conclusion
• WHO use of imputation:– Correction for definitional differences, application
of WHO standards, known biases– Production of regional aggregates– Generation of missing values for countries
• Recommendations for CCSA– General principles for imputation– Methods context and subject specific– Transparency and replicability– Country endorsement of methods not values