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Hi.

Have you checked the results of your code for Fisher's Exact Test? I don't think it produces correct results.

Here's a utility that produces results identical to those I calculate: http://www.exactoid.com/fisher/index.php

This expression at the beginning of your code seems odd:

$test = $a*($a+$b+$c+$d ) - ($a+$b)*($a+$c);
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It simplifies to: $test = $a*$d - $b*$c;

I don't follow why you have this:

return 1 if $test < 0 and $ts;
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For example, if a = 1, b = 50, c = 10 and d = 5, P(one-sided) = P(two-sided) = 1.4386e-07, not 1.

Nevertheless, thanks for the tip about calculating factorials only once. Let me know if I've misunderstood something.

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