A measure of the extent to which the different types in a population are unequally common. A value of 0 is attained if there is only one type in the population. One index is the Shannon index:
where there are k types and pj is the proportion of type j. The base of the logarithm is arbitrary, but the usual choice is 2 (so that log2 (½)=−1, log2 (¼)=−2, etc.) in which case the index may alternatively be referred to as the entropy of the classifying variable. An alternative is the Simpson index:
- Berkeley, George (1685–1753)
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- Berkson’s paradox
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- Bernoulli
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- Bernoulli, Daniel (1700–82)
- Bernoulli distribution