Diversity index#Simpson index

The Simpson index was developed in 1949 by Edward H. Simpson to describe the diversity ( cf. biodiversity) and is adjacent to the Shannon index and evenness calculated from one of the most commonly used diversity indices. He expresses the probability that two not the same kind belong from all individuals of a recording randomly selected individuals. These are the probabilities of selecting a certain type and that type select again (applies to the first individual is not more to choose from) multiplied and then summed this product for all species.

Simpson index is therefore calculated as follows:

Wherein the number of individuals of a species, the total number of individuals representing. D is equal to 0, if all individuals of the same kind belong to, in other words, there are no diversity. The greater the diversity, the more D approaches the first

In relevés not individuals are usually counted but area shares ("Coverage " ) is estimated for each species. Thus it is now the likelihood not to be found at two points randomly selected in a receiving surface in the same way. With coverage values, rather than individuals simplifies the formula, because the probabilities for the first and second point are the same:

Where the proportion of the species reproduces in the sum of all individual coverages.