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Eek! I knew someone would say something like
this!
--Original Message-- From: Randy King <randyk@ims.com>Date: 09 November 1998 19:19 >I'm late in my emails again, hope this hasn't been beaten to death >already. I just can't leave it alone.... > >At 11:52 PM 11/5/98 EST, Philidor11@aol.com wrote: >>'Say the ratio of maniraptorans living in the K to those living in the J was >>A:B; >>Say the ratio of the chances of an indiv living in the K ever being found to >>that of one in the J is C:D; >>The ratio of the chances of a maniraptoran we have found coming from the K >>to from the J is (A/B)*(C/D). >>The probability of any maniraptoran we have found coming from the K is 1/(1 >>+ 1/ ((A/B) * (C/D)) ). > >I think this is incorrect. I believe the ration of maniraptoran in K to J >would be (AC:BD). But that's the same as (A/B)*(C/D). As for the rest of it, well, you may well be right, I'm not even going to check it, because the chances of throwing heads 170 times in a row is still incredibly small, even with a coin that lands heads 95% of the time. >The probability of a given maniraptoran coming from K >would be AC/(AC+BD). The probability of N given maniraptorans coming from K >would be [AC/(AC+BD)]^N. > >> >>The chance of N maniraptoran fossils all appearing after Archaeopteryx is >>this _expression_ raised to the power of N.' > >Assuming Archie came from the JK border. No, I did say much the same applies wherever you take the line, just a slightly different question. >There are too many assumptions >being made to draw definite conclusions. Starting with, distribution of >creatures we've found from J or K isn't an independent variable, but very >dependent on the geography. It's the same planet! And nothing's definite in probability - you still end up with another probability. The two assumptions I make are that, worldwide, the fossilisation llikelihood ratio between J and K is such and such (slot in your choice) and the actual number of animals-ratio was (again, make your choice). I don't think making those assumptions is unreasonable. The answer is just another probability. > >Where are you trying to go - and who was it that's going?? I'm going to prove the maniraptorans are birds - and you're all going eventually! >-Randy, mathematician at large. BUT - thanks very much for taking the trouble to work through it. Regards, JJ |