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Many animals, including humans, tend to live in groups, herds, flocks, bands, packs, shoals, or colonies (hereafter: groups) of conspecific individuals. The size of these groups, as expressed by the number of participant individuals, is an important aspect of their social environment. Group size tend to be highly variable even within the same species, thus we often need statistical measures to quantify group size and statistical tests to compare these measures between two or more samples. Group size measures are notoriously hard to handle statistically since groups sizes typically follow an aggregated (right-skewed) distribution: most groups are small, few are large, and a very few are very large. Statistical measures of group size roughly fall into two categories. ==Outsiders' view of group size== * Group size is the number of individuals within a group; * Mean group size , the arithmetic mean of group sizes averaged over groups; * Confidence interval for mean group size; * Median group size, the median of group sizes calculated over groups; * Confidence interval for median group size. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「group size measures」の詳細全文を読む スポンサード リンク
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