Talk:Morisita's overlap index

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Context

The article starts with this:

Morista's overlap index is used to compare overlap among samples (Morista 1959).

This formula is based on the assumption that increasing the number of samples will increase the diversity because it will include different habitats (i.e. different faunas).

The words "habitats" and "faunas" appear near the end of the second sentence, and suggest that what we're taking samples of is animals. Not widgets coming off an assembly line, not apples, not web pages, not customers of a grocery store chain, but animals. Yet it doesn't tell us that. It's as if it is expected the reader somehow knows that without being told. I'd fix it if I knew anything about the subject.

Also, I don't find any reference to a paper by Morista published in 1959. What article title, what journal, etc.? Michael Hardy (talk) 18:00, 26 June 2009 (UTC)[reply]

The man's name is Morisita, not Morista. Here is a reference to one of his articles: Morisita, M. (1959). Measuring of the dispersion and analysis of distribution patterns. Memoires of the Faculty of Science, Kyushu University, Series E. Biology. 2: 215-235. —Preceding unsigned comment added by 69.14.220.167 (talk) 18:41, 27 October 2009 (UTC)[reply]

X and Y ?

What are the quantities denoted by capital X and capital Y? The article fails to say. Michael Hardy (talk) 01:43, 12 December 2010 (UTC)[reply]

Also, we find this:

D_x and D_x - Simpson's index values for species i

That doesn't make sense. The index i is something that runs from 1 through S in the numerator. Thus:

{\begin{aligned}C_{D}&={\frac {2\sum _{i=1}^{S}x_{i}y_{i}}{(D_{x}+D_{y})XY}}\\[8pt]&={\frac {2(x_{1}y_{1}+x_{2}y_{2}+\cdots +x_{S}y_{S})}{(D_{x}+D_{y})XY}}.\end{aligned}}

In the first term in the numerator, i = 1.
In the second term in the numerator, i = 2.
In the third term in the numerator, i = 3.
etc.........
In the last term in the numerator, i = S.

But what is i in the denominator? And why is it being asserted that some expressions in the denominator correspond to "species i" when we don't even see an i in the denominator? Michael Hardy (talk) 01:49, 12 December 2010 (UTC)[reply]

X=\sum _{i=1}^{S}x_{i}\,.

Y=\sum _{i=1}^{S}y_{i}\,.

JRSpriggs (talk) 08:33, 12 December 2010 (UTC)[reply]