Biodiversity Simpson Index Calculator — Formule
## Simpson Diversity Index
The Simpson Index measures the probability that two randomly selected individuals belong to different species. Higher values mean greater diversity.
### Formula
**D = Sum of [n(n-1)] / [N(N-1)]**
Where n is the count of each species and N is the total count. D ranges from 0 to 1, where 0 is infinite diversity and 1 is no diversity. The complement (1-D) is more intuitive: higher values mean more diversity.
The Simpson Index measures the probability that two randomly selected individuals belong to different species. Higher values mean greater diversity.
### Formula
**D = Sum of [n(n-1)] / [N(N-1)]**
Where n is the count of each species and N is the total count. D ranges from 0 to 1, where 0 is infinite diversity and 1 is no diversity. The complement (1-D) is more intuitive: higher values mean more diversity.
Exemple Résolu
A forest plot has 40 oaks, 25 maples, 20 birches, and 15 pines.
- Total N = 40 + 25 + 20 + 15 = 100
- Sum n(n-1) = 40x39 + 25x24 + 20x19 + 15x14 = 1560 + 600 + 380 + 210 = 2750
- D = 2750 / (100 x 99) = 2750 / 9900 = 0.2778
- Diversity (1-D) = 1 - 0.2778 = 0.7222
- Reciprocal = 1/0.2778 = 3.60