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Randomness and Probability (off topic)

John Bois wrote:
> Given roughly equal diversity before, random action should yield
> 50/50--or do I misunderstand how this statistical process works?

It would seem to me that, if you could put a precise probability value to
something, then it isn't random. Tossing a coin is a random action *each time
you do it*, however there are only two possible outsomes (technically not true -
the coin could land on its edge and stay there!), each mutually exclusive, and
each throw does not affect the next one at all. Given only two possible
outcomes, and equal likelihood, then over an infinite number of tosses the stats
should approach 50/50. Randomness only comes into play in the short term. The
results of an infinite number of tosses will not be random (provided there
actually is equal likelihood for the two outcomes - the air resistance of the
design on one side of the coin may subtly affect the toss so as to favour one
side over the other in a large number of tosses). 

If you start talking about random variables playing havoc with something as
complex as an ecosystem, however, then there are clearly more than just two
outcomes, and anything affected by these random interplay of variables is not an
independant event. It can (and usually will) feed back into the system, creating
further chaos. Suggesting that the interplay of random variables (that is, more
random than usual) into an ecosystem will result in equal measures of extinction
in two separate groups is far too simplistic for my tastes.


Dann Pigdon                   Australian Dinosaurs:
GIS Archaeologist           http://dannsdinosaurs.terrashare.com
Melbourne, Australia        http://www.alphalink.com.au/~dannj/