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Suppose I have a set of 40 variables

{A, B, C...}

I want to count the number of possible correlations for n variables. For example, if n=2

I have

40(40-1)/2=780 correlations

How do I do it for n > 2?

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Well, how did you do it for $n=2$? –  Pedro Tamaroff Sep 6 '12 at 23:51

1 Answer 1

up vote 1 down vote accepted

What you did for $n=2$ works for $n\gt2$ (as Peter implies in a comment). For $n=3$, you get $$(40)(40-1)(40-2)/(1)(2)(3)$$ for $n=4$, $$(40)(40-1)(40-2)(40-3)/(1)(2)(3)(4)$$ and so on.

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I'd vote you up but I lack the rep... Thanks! :) –  Nik Sep 7 '12 at 0:35

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