An ecological fallacy (or ecological inference fallacy, also referred to as the fallacy of division) is a logical fallacy in the interpretation of statistical data in an ecological study, whereby inferences about the nature of individuals are based solely upon aggregate statistics collected for the group to which those individuals belong. In epidemiology, the ecological fallacy is committed when a correlation observed at the population level is assumed to apply at the individual level. This fallacy assumes that individual members of a group have the average characteristics of the group at large. However, statistics that accurately describe group characteristics do not necessarily apply to individuals within that group. For a mathematical explanation of this see how variability of individuals is much greater than the variability of their mean.
Stereotypes, which assume that groups are homogeneous, are one form of ecological fallacy. For example, if a particular group of people are measured to have a lower average IQ than the general population, it is an error to assume that any or all members of that group have a lower IQ than the general population. In fact, any given individual from that group may have a lower than average IQ, average IQ, or above average IQ compared to the general population.
My Take - This is worth exploring as it is used by the greenies...and the left as a whole... all the time. RK