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Multilevel Modeling

5. Desiderata for Multilevel Research

Some core concepts are intrinsic to adopting a multilevel perspective and are discussed in this section, including:

  • Contextual and Compositional Sources of Variation;
  • Contextual Heterogeneity;
  • Individual Heterogeneity;
  • Individual/Contextual Interaction;
  • Multiple Hierarchical Contexts;
  • Changing People/ Changing Places;
  • Interrelated Outcomes; and
  • Overlapping Contexts.

Contextual and compositional sources of variation Evidence for variations in poor health between different settings or contexts can be due to factors that are intrinsic to, and are measured at, the contextual level. In other words, the variation can be due to what can be described as contextual, area, or ecological effects. Alternatively, variations between places may be compositional, i.e., certain types of people who are more likely to be in poor health due to their individual characteristics happen to live in the same places.

The Research Question here is not whether variations between different settings exist (they usually do), but what is their source, i.e., are the variations across places compositional or contextual?

The notions of contextual and compositional sources of variation have general relevance and they are applicable whether the context is administrative (e.g., political boundaries), temporal (e.g., different time periods), or institutional (e.g., schools or hospitals). The research question focused on this core concept would be: are there significant contextual differences in health between settings (such as neighborhoods), after taking into account the individual compositional characteristic of the neighborhood?

Contextual heterogeneity

Beyond disentangling the contextual and compositional sources of variation, contextual differences may be complex such that it may not be the same for all types of people. For example, while neighborhood contexts may matter for the health outcomes of one population group (e.g., low social class), it may not have any influence upon the health status of other groups (e.g., high social class).

The Research Question in this case is: are the contextual neighborhood differences in poor health different for different types of population groups?

Individual heterogeneity

Within particular contexts, one group’s health experience may be more or less variable than the other, over and above the average differences. For example, people of low social class, in addition to being contextually heterogeneous, may experience more variability compared to other groups.

The Research Question is: are individual differences in poor health different for different types of population groups?

Individual/contextual interaction

Contextual differences, in addition to people’s characteristics, may also be influenced by the different characteristics of neighborhoods. Stated differently, individual differences may interact with context. For example, poor people (individual characteristic) may experience different levels of health depending upon the poverty levels (place characteristic) of the area in which they live.

The Research Question of interest is: what is the average relationship between individual poor health and neighborhood-level socioeconomic characteristics, and does the effect of neighborhood-level socioeconomic characteristics on individual health differ for different types of individuals based on their demographic and socioeconomic characteristics?