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*To*: dinosaur@usc.edu*Subject*: Re: Extinction*From*: John Bois <jbois@umd5.umd.edu>*Date*: Wed, 4 Dec 1996 14:20:09 -0500 (EST)*Reply-to*: jbois@umd5.umd.edu*Sender*: owner-dinosaur@usc.edu

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 wrong?

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