A community dominated by one or two categories is considered to be
less diverse than one in which several different categories have a similar
abundance. Simpson's Diversity Index is a measure of diversity which takes
into account the number of categories present, as well as the relative
abundance in each category. As the richness of categories and evenness
increase, so diversity increases. Simpson's Diversity Index (D) is given by the formula above using the total number (n) of values of a particular category and the total number (N) of values of all categories.

D can range from 0 (no diversity) to 1 (infinite diversity)

Note: the areas must be sampled using quadrats placed randomly or systematically

D can range from 0 (no diversity) to 1 (infinite diversity)

Note: the areas must be sampled using quadrats placed randomly or systematically

Example: analysis of the diversity of stores in a neighborhood

Let's calculate Simpson's Index for the types of stores in a neighborhood: the list of categories of shop within each quadrat, as well as the number of shops in each category should be noted. There is no necessity to be able to identify all the shops, provided they can be distinguished from each other.

As an example, let us work out the value of D for a single quadrat sample. Of course, sampling only one quadrat would not give you a reliable estimate of the diversity of the shops in the entire city. Several samples would have to be taken and the data pooled (ie: extrapolated) to give a better estimate of overall diversity. The quadrat sampled gives us the following results:

Let's calculate Simpson's Index for the types of stores in a neighborhood: the list of categories of shop within each quadrat, as well as the number of shops in each category should be noted. There is no necessity to be able to identify all the shops, provided they can be distinguished from each other.

As an example, let us work out the value of D for a single quadrat sample. Of course, sampling only one quadrat would not give you a reliable estimate of the diversity of the shops in the entire city. Several samples would have to be taken and the data pooled (ie: extrapolated) to give a better estimate of overall diversity. The quadrat sampled gives us the following results:

n |
||
---|---|---|

Using the formula given above, we can calculate the Simpson's
Index of Diversity D = 0.71

D can range from 0 (no diversity) to 1 (infinite diversity): we can therefore conclude that the quadrat sampled has a relatively high variety of shops.

D can range from 0 (no diversity) to 1 (infinite diversity): we can therefore conclude that the quadrat sampled has a relatively high variety of shops.