手法を比較

	E-I Index	Homophily Analysis	Isolation Index
分野	Sociology	Sociology	Sociology
系統	Process / pipeline	Process / pipeline	Process / pipeline
提唱年	1988	1954 (concept); 2001 (synthesis)	1954
提唱者	David Krackhardt & Robert Stern	Lazarsfeld & Merton (concept); McPherson, Smith-Lovin & Cook (synthesis)	Wendell Bell (formalization of P* indices)
種類	Index of the relative balance of between-group versus within-group ties	Measurement of similarity-based tie formation	Exposure-dimension segregation index
原典	Krackhardt, D., & Stern, R. N. (1988). Informal networks and organizational crises: An experimental simulation. Social Psychology Quarterly, 51(2), 123–140.	McPherson, M., Smith-Lovin, L., & Cook, J. M. (2001). Birds of a feather: homophily in social networks. Annual Review of Sociology, 27, 415–444.	Bell, W. (1954). A probability model for the measurement of ecological segregation. Social Forces, 32(4), 357–364.
別名	EI index, external-internal index, Krackhardt-Stern E-I ratio, E/I ratio	homophily measurement, assortative mixing analysis, birds-of-a-feather analysis, tie-similarity analysis	P* isolation index, interaction index, exposure index, Bell isolation index
関連	5	4	5
概要	The external-internal (E-I) index, introduced by Krackhardt and Stern, measures the extent to which the ties of a group point outward to other groups versus inward to its own members. It is the number of between-group (external) ties minus the number of within-group (internal) ties, divided by the total number of ties. Ranging from −1 (all ties internal, perfect insularity) to +1 (all ties external), it is a compact summary of homophily and group closure that can be computed for a whole network, for each group, or for each node.	Homophily analysis quantifies the tendency of similar individuals to form ties — the principle that 'birds of a feather flock together'. It compares the rate at which people connect with others who share an attribute (race, gender, age, education, attitudes) against what would be expected by chance, distinguishing the homophily that arises merely from group sizes from the genuine, behavior-driven preference for similar others.	The isolation index measures the exposure dimension of segregation: the extent to which members of a minority group are exposed only to one another rather than to members of other groups. It answers the question 'what is the own-group share of the typical neighbor (or classmate, or coworker) that a member of the focal group encounters?' Unlike evenness measures, it depends on the relative size of the group as well as its spatial distribution.