[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

*To*: dinosaur@usc.edu*Subject*: Re: Extinction (of marbles)*From*: stevet@shelby.net (Stephen Throop)*Date*: Wed, 4 Dec 1996 14:22:41 -0500 (EST)*Reply-to*: stevet@shelby.net*Sender*: owner-dinosaur@usc.edu

Stan Friesen wrote: > Try a different model: 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)? [......] > > And yet this is what happened at the K/T. Some non-random > > causative force was at work. > > This is debatable, at best. This is what you have to demonstrate: > thet there *was* indeed a non-random causative force. To do so you > must actually perform a statistical test of the observed extinction > pattern against the predicted extinction pattern. Marbles! Oh boy! I think the easiest approach is to calculate the chances that any red marble would be among the 25% that survive, not whether all reds would be among the 75% that don't. If you pick a single "survivor" from a box with 100 red marbles and 600 others, the odds are 6 to 1 that it won't be red. However, if you pick 4, odds are slightly better than even, about 20 to 17, that one will be a red. If you pick 7 (1% survival), odds are about 2 to 1 that you will have a red. If you pick 70 (10% survival), odds are about 90 thousand to 1 that you will have a red. If you pick 175 (25% survival), odds are 44 trillion to 1 that you will have at least one red. Did I figure out the math right? If I have applied the marble analogy correctly, it sounds as if the KT extinctions were not random. - Stephen Throop

- Prev by Date:
**Re: Extinction** - Next by Date:
**beaks** - Previous by thread:
**Re: stats** - Next by thread:
**Re: Extinction (of marbles)** - Indexes: