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On Tue, 3 Dec 1996, Stan Friesen wrote:
>... in the Lancian deoposits there were about 10-12
> species of dinosaurs and more than 20 species of mammals, perhaps as
> many as 30. Thus 300 green marbles and 100 red is more like reality.
> Now add 50 pink marbles, and 150 blue marbles, and 100 yellow ones,
> and some more of several additional colors.
> Now, select 75% of the marbles. What is the probability that all of
> *at* *least* *one* color are chosen (not necessarily red)? [From a
> statistical point of view, this si the correct question, not the
> probability of choosing all red]. There is actually quite a high
> probability that at least one group will be completely wiped out. But
> the mammals, being the most diverse group, are the least likely to
> buy the farm.
Where am I going wrong? Using your "data" I made 72 little slips of
paper and colored 30 green (mammals), 12 red (dinos), 5 pinks, 15 blues,
10 yellows. Then I took out 30%--and your 75% extinction rate is
high. In Ward's Nov. _Science_ paper 70% is cited so I used that--or 22
slips at random. I simulated 10 K/T extinctions. Only one species became
extinct (Yellow) and that only happened once!!! By chance alone, dinos
did very well: of their 12 "species" the following numbers surived the
ten successive K/Ts--8,8,5,7,5,3,7,5,4,6.
I know it can't be that simple. Like I said, where am I going