手法を比較

	E-I Index	Isolation Index
分野	Sociology	Sociology
系統	Process / pipeline	Process / pipeline
提唱年	1988	1954
提唱者	David Krackhardt & Robert Stern	Wendell Bell (formalization of P* indices)
種類	Index of the relative balance of between-group versus within-group ties	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.	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	P* isolation index, interaction index, exposure index, Bell isolation index
関連	5	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.	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.