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UNDERSTANDING MULTILEVEL ANALYSIS Comic concepts for epidemiologists

UNDERSTANDING MULTILEVEL ANALYSIS Comic concepts for epidemiologists. Juan Merlo Department of Community Medicine Lund University, Malmö SWEDEN. Learning Objectives. To understand the concept of levels of analysis

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UNDERSTANDING MULTILEVEL ANALYSIS Comic concepts for epidemiologists

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  1. UNDERSTANDING MULTILEVEL ANALYSIS Comic concepts for epidemiologists Juan Merlo Department of Community Medicine Lund University, Malmö SWEDEN Merlo J. 2002-05-05

  2. Learning Objectives • To understand the concept of levels of analysis • To intuitively understand the principles of multilevel regression techniques • To intuitively understand multilevel epidemiological concepts like • Different levels of variation • Intra-class correlation • Fixed and random effects • Compositional and contextual factors Merlo J. 2002-05-05

  3. Performance Objectives After this lecture the student will be able • To recognize multilevel structures • To use basic epidemiological multilevel concepts Merlo J. 2002-05-05

  4. Many hierarchical (MULTILEVEL) data structures exist which are relevant to Public Health, in which more than one level may influence individual health. Multilevel modelling is a statistical technique for the analysis of hierarchical (MULTILEVEL) data. Merlo J. 2002-05-05

  5. Understanding multilevel analysis Merlo J. 2002-05-05

  6. To understand multilevel analysis let us create an example using -----Places----People---Mouths --Teeth-Caries (a demineralization of the tooth surface caused by bacteria.) Merlo J. 2002-05-05

  7. Other multilevel examples could be: • City areas and individual blood pressure level J Epidemiol Community Health 2001; 55: 323-. • Hospitals and individual survival after heart failure J Epidemiol Community Health 2001; 55:791- • Neighbourhoods and individual use of medication American Journal of Epidemiology 2002 Merlo J. 2002-05-05

  8. The multilevel concept Caries A population of caries Something important is being ignored….. Merlo J. 2002-05-05

  9. The multilevel concept The tooth A population of teeth Something important is being ignored….. Merlo J. 2002-05-05

  10. The multilevel concept The mouth A population of mouths Something important is still being ignored ….. Merlo J. 2002-05-05

  11. The multilevel concept A population of persons Something important is still being ignored ….. Merlo J. 2002-05-05

  12. The multilevel concept A population of places ………etc……. Merlo J. 2002-05-05

  13. The multilevel concept Level 5: Place • AT EACH LEVEL THERE ARE • Differences (random effects) • Mean characteristics (fixed effects) Level 4: individual Level 3: mouth Level 2: tooth Level 1: caries Merlo J. 2002-05-05

  14. The multilevel concept • DIFFERENT LEVELS OF AGGREGATION • RELEVANT LEVELS OF ANALYSIS? • AGGREGATION /DISAGREGATION BIAS Level: teeth Level: caries Level 1: teeth Level: mouth Level: individual Level 2: mouth Level: Place Merlo J. 2002-05-05

  15. The multilevel concept ECOLOGICAL ANALYSIS Level 1: Place Level: caries Level: teeth Level: mouth Level: individual Merlo J. 2002-05-05

  16. The multilevel concept • The multilevel way of thinking is an old way in epidemiology • Multilevel regression techniques (Hierarchic regression, mixed models) are only a propper procedure to analyse multilevel questions Why do we need multilevel regression techniques? Merlo J. 2002-05-05

  17. ”CLUSTERING” If mouths have effect on teeth health, the health of the teeth in the same mouth would be similar…also teeth’s health would be CLUSTERED INSIDE THE MOUTHS If there is a ”CLUSTERING” of individual in areas (teeth’s health in mounths)….we need multilevel regression techniques Merlo J. 2002-05-05

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