"Erica So" <[EMAIL PROTECTED]> wrote in message 
news:<[EMAIL PROTECTED]>...
> To explain why my data are less than one, let me tell u what I do in my
> experiment. My experiment is a kind a ecological survey, which involves
> counting the number of different animal species in different algae species.
> Since the area of algae species are varied, so I will calculate the density
> instead of number of individuals.
> 
> eg 6 animal Y was found in 100cm2 algae Z
>      So, the data (density) that involves in the Chisq = 6/100 = 0.06, but
> not 6 individuals. That's why my data are usually less than 1 due to
> dividing the area.
> [...]

Why not do a loglinear analysis of the raw counts, without converting
them to densities? Variability of both the areas of the algae species
and the prevalences of the animal species will show up as main effects
and will not change the interaction terms, which are what you're
interested in.
.
.
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