230px|A group acts as a social environment of individuals: a flock of nine common cranes. 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 people/etc in a group such as 8 groups of 9 people in each one, 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. Crowding is the size (the number of individuals) of a group that a particular individual lives in (equals to group size: 1 for a solitary individual, 2 for both individuals in a group of 2 , etc.). Practically, it describes the social environment of one particular individual. This was called Individual Group Size in Jovani & Mavor's (2011) paper.; Mean crowding, i.e. the arithmetic mean of crowding measures averaged over individuals (this was called "Typical Group Size" according to Jarman's 1974 terminology); Confidence interval for mean crowding. Imagine a sample with 3 groups, where group sizes are 1, 2, and 6 individuals, respectively, then mean group size (group sizes averaged over groups) equals ; mean crowding (group sizes averaged over individuals) equals . Reiczigel et al. (2008) discuss the statistical problems associated with group size measures (calculating confidence intervals, 2-sample tests, etc.) and offer a free statistical toolset (Flocker 1.1).
230px|A group acts as a social environment of individuals: a flock of nine common cranes. 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 people/etc in a group such as eight groups of nine people in each one, 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. Crowding is the size (the number of individuals) of a group that a particular individual lives in (equals to group size: one for a solitary individual, two for both individuals in a group of two , etc.). Practically, it describes the social environment of one particular individual. This was called Individual Group Size in Jovani & Mavor's (2011) paper.; Mean crowding, i.e. the arithmetic mean of crowding measures averaged over individuals (this was called "Typical Group Size" according to Jarman's 1974 terminology); Confidence interval for mean crowding. Imagine a sample with three groups, where group sizes are one, two, and six individuals, respectively, then mean group size (group sizes averaged over groups) equals ; mean crowding (group sizes averaged over individuals) equals . Reiczigel et al. (2008) discuss the statistical problems associated with group size measures (calculating confidence intervals, two-sample tests, etc.) and offer a free statistical toolset (Flocker 1.1).
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8 groups of 9
eight groups of nine
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1
one
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2
two
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2
two
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3
three
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1, 2, and 6
one, two, and six
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2-sample
two-sample