Heterogeneity refers to the properties of a sample group or set. The term is used when a sample is composed of items or individuals that are different from one another. Heterogeneity signifies diversity within a group or sample. This is the opposite of homogeneity when samples are more alike than different.
For instance, in a research study a group that is formed from a random sampling of professionals, blue-collar workers, men, women, assorted ethnic groups, etc., would be considered a heterogeneous sample. However, a group of persons who are of the same ethnic group, educational level, age, and gender would be considered a homogeneous group.