Shannon-Wiener index of diversity(information index) A measure derived from information theories developed by Claude E. Shannon and Norbert Wiener and published in 1949 by Shannon and Warren Weaver, which is used by ecologists when a system contains too many individuals for each to be identified and examined. A small sample is used; the index (D) is the ratio of the number of species to their importance values (e.g. biomass or productivity) within a trophic level or community. D = − Σ^s_ip_ilogp_i, where s is the total number of species in the sample, i is the total number of individuals in one species, p_i (a decimal fraction) is the number of individuals of one species in relation to the number of individuals in the population, and the log is to base-2 or base-e.

Shannon–Wiener index of diversity (information index) A measure used by ecologists when a system contains too many individuals for each to be identified and examined. A small sample is used; the index (D) is the ratio of the number of species to their importance values (e.g. biomass or productivity) within a trophic level or community. D = −Σ^s_ip_i log p_i, where s is the total number of species in the sample, i is the total number of individuals in one species, p_i, (a decimal fraction) is the number of individuals of one species in relation to the number of individuals in the population, and the log is to base-2 or base-e.

Shannon-Wiener index of diversity (Shannon-Weaver index, information index) A measure, derived from information theories developed by Claude E. Shannon and Norbert Wiener and published in 1949 by Shannon and Warren Weaver, that is used by ecologists when a system contains too many individuals for each to be identified and examined. A small sample is used; the index is the ratio of the number of species to their importance values (e.g. biomass or productivity) within a trophic level or community.