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Which statistical test?

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Which statistical test?

Postby qwertyuiop12345 » Fri Sep 18, 2009 2:22 pm

I have three different shorelines, and three different heights along each shore (high, middle, low). For each of the heights at each of the shores I have quantities of two types of organism. I want to examine the quantities of the two organisms to see a) if they differ in abundance at the three heights on the shore, b) if they differ in abundance across the three shores and c) if there are any interactions between the two species which are affecting their abundance. I have lots of data and would like to know which statistical test is best to use to investigate these things. Thank you very much!
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Postby JackBean » Fri Sep 18, 2009 2:54 pm

I'm not sure, whether I understand, what data you have and what is your point, but to me it sounds like work for 2-way ANOVA?
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Postby qwertyuiop12345 » Fri Sep 18, 2009 3:00 pm

Yes I think so as well, I'm just looking over 2 way ANOVA. Something like:

For shores 1, 2 and 3:

--------------------High Shore ------Middle Shore ----Low Shore
Organism 1 -------- 363 -------------- 245-------------755
Organism 2 -------- 222 -------------- 341-------------457

This shows the abundance of each of the two organisms at varying shore heights, but it doesn't compare them across shores. I hate statistics...
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Postby JackBean » Fri Sep 18, 2009 3:24 pm

Actually, 2WA would compare them across shores, but it would also investigate, whether there is some aditive influence of organism and shore (like, if you change from high to low AND from 1 to 2), so thats probably not, what you need, right?
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Postby qwertyuiop12345 » Sat Sep 19, 2009 12:48 pm

It's OK, I used a 2 way ANOVA with abundance of organism 1 as the dependent variable and shore height and shore 1, 2, 3 as the fixed factors in SPSS. I then did the same for organism 2.

Thanks for your help!
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