Stereotype bias includes misjudging within-group variability, not just mean differences

Evidence

The second sort of inaccuracy focuses on the perceiver’s estimate of the within-group variability of individuals along the attribute continuum. One may underestimate or overestimate the degree to which individuals who are members of the groups are dispersed along the continuum, and this error may characterize perceptions of one of the groups more than perceptions of the other. This sort of error is known as dispersion inaccuracy. — , Rudman, Laurie A - On the Nature of…, 857

A useful analogy in thinking about these two forms of inaccuracy derives from statistics, where the significance of a group difference depends on the size of the mean difference between the groups, relative to the withingroup(s) variability. In the stereotyping literature, this ratio has come to be known as the metacontrast ratio (Oakes, Haslam, & Turner, 1994; Turner et al., 1987). The exaggeration of group differences in stereotypic beliefs can occur either when the stereotypic mean difference between the groups along the attribute continuum is overestimated or when the within-group dispersion of individuals along the continuum is underestimated. On the other hand, one might also underestimate group differences along the continuum, either by underestimating the magnitude of the mean difference between the groups or by overestimating the within-group dispersion of individuals along the continuum. — , Rudman, Laurie A - On the Nature of…, 858

Categorization

• DEFINE: Introduces dispersion inaccuracy, a distinct and easily overlooked axis of stereotype error separate from mean shifts.
• XREF: Relates to the outgroup homogeneity effect in stereotype research - perceived homogeneity as a distinct error type. — connects to: Small derogatory perceived differences suffice to justify group advantage — John T. Jost and Jim Sidanius, Political Psychology: Key Readings, 3418; Abstract-level middle-cluster stereotypes mask sharp subtype splits within a group. — Susan T. Fiske et al., A Model of (Often Mixed) Stereotype…, 292
• corroborated: 5 independent passages support this claim — , Rudman, Laurie A - On the Nature of…, 857; , Rudman, Laurie A - On the Nature of…, 858