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| '''Simpson's diversity index''' (also known as Species diversity index) is a measure of diversity. In ], it is often used to quantify the ] of a habitat. It takes into account the number of ] present, as well as the relative abundance of each species. The Simpson index represents the probability that two randomly selected individuals in the habitat belong to the same species. | |||
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| == Overview == | |||
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| For ] species the percentage cover in a quadrate is usually used, for ] species, for example in a river, the number of ] of a species is used. The reason percentage cover is used is because it is usually very difficult to count all the individual grass plants. | |||
| The ] for the Simpson index is: | |||
| :<math>D=\frac{\sum_{i=1}^S n_i(n_i-1)}{N(N-1)}</math> | |||
| Where ''N ''is the total percentage cover or total number of organisms and ''n'' is the percentage cover of a species or number of organisms of a species. | |||
| When using the Simpson Index for lower numbers, misleading results can be obtained, with obviously less diverse areas having a higher index than they should. One way around this when studying on land is to include bare earth as an extra species, which yields more realistic results. | |||
| The Simpson index was first proposed by the British statistician ] in a paper in '']'' in ]. | |||
| ==See also== | |||
| *] | |||
| *] | |||
| *] | |||
| == References == | |||
| * ] (1949) Measurement of diversity. '']'' '''163''':688 see http://www.wku.edu/~smithch/biogeog/SIMP1949.htm | |||
| == External links == | |||
| * http://www.countrysideinfo.co.uk/simpsons.htm | |||
| * http://www.snr.missouri.edu/NR211/topics/simpsons.html | |||
| * http://members.cox.net/bennowak/environment/envla/simpdivindex.htm | |||
| ] | |||
| ] | |||
| ] | |||
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