手法を比較

	E-I Index	Homophily Analysis
分野	Sociology	Sociology
系統	Process / pipeline	Process / pipeline
提唱年	1988	1954 (concept); 2001 (synthesis)
提唱者	David Krackhardt & Robert Stern	Lazarsfeld & Merton (concept); McPherson, Smith-Lovin & Cook (synthesis)
種類	Index of the relative balance of between-group versus within-group ties	Measurement of similarity-based tie formation
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.
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
関連	5	4
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.