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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 Juan Merlo Department of Community Medicine Lund University, Malmö SWEDEN Merlo J. 2002-05-05
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
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
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
Understanding multilevel analysis Merlo J. 2002-05-05
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
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
The multilevel concept Caries A population of caries Something important is being ignored….. Merlo J. 2002-05-05
The multilevel concept The tooth A population of teeth Something important is being ignored….. Merlo J. 2002-05-05
The multilevel concept The mouth A population of mouths Something important is still being ignored ….. Merlo J. 2002-05-05
The multilevel concept A population of persons Something important is still being ignored ….. Merlo J. 2002-05-05
The multilevel concept A population of places ………etc……. Merlo J. 2002-05-05
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
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
The multilevel concept ECOLOGICAL ANALYSIS Level 1: Place Level: caries Level: teeth Level: mouth Level: individual Merlo J. 2002-05-05
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
”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