Aggregation

Aggregation is the process by which data are collected at a different level from the level of greatest interest. Data are aggregated because they are more available at the group level. For example, crime statistics are available from urban centers but, in general, not from every citizen of the city. Attempts are then made to identify exposure-response relationships among different aggregates. The ECOLOGICAL FALLACY is the false conclusion that a result about groups, or aggregates, of individuals applies to the individuals within these aggregates. Because each aggregate contains individuals who differ from each other, the conclusion about the aggregate does not apply to each of its member individuals.