3.4. Indexes of aggregation
1. Coefficient of dispersion:
2. Mean crowding 
(Lloyd 1967) is equal to the mean number of "neighbors" in the same quad:
| Sample No. | No. of individuals (N) |
No. of neighbors (N-1) | N(N-1) |
| 1 | 5 | 4 | 20 |
| 2 | 3 | 2 | 6 |
| 3 | 0 | -1 | 0 |
| 4 | 1 | 0 | 0 |
| 5 | 7 | 6 | 42 |
| Total | 16 | - | 68 |
It means that the mean number of "neighbors" is = 4.25.
Note: mean crowding has biological sense only if the size of each quad corresponds to "interaction distance" among individuals.
Consider probability distribution p(i) = the proportion of samples with i individuals. Then:
For a random (poisson) distribution, CD=1, and thus, = m.
3. Lloyd (1967) suggested a "patchiness" index: /m, which is 1 for a random distribution, > 1 for aggregated distributions, and <1 for regular distributions. However it does not make more sense than CD.
