[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: EARLY EVOLUTION OF 'BIRDS'
In a message dated 11/6/98 12:19:53 PM Eastern Standard Time,
I'm following your argument slowly. The Law of Averages, or regression to the
mean, says that if you start flipping a coin and heads come out 9 times in a
row, and then you keep flipping thru the eons, sometime before the sun burns
out or blows up or both you will probably have 9 more tails than heads. But
don't count on it. The idea that 9 heads in a row affects the next flip is
called 'Gambler's Fallacy' and is a major money maker.
The kind of meta-analysis you're talking about was recently used by Shafer et
al at Harvard to look at 20 years, give or take, of pathological gambling
prevalence studies. He observes the inadequacies of each approach used, then
tries to combine them to draw a conclusion that pathological gambling has
increased in recent years. His reasoning is that because some inadequate
studies before a certain date he picked produced some results just outside the
high end of the range of the inadequate studies after that date, therefore
pathological gambling has increased. The difference in ranges is in the
hundredths of a percent.
More relevantly, your mickles had better had some validity to begin with. I
don't think inadequate results gain strength in numbers. Validity in this
case refers to the likelihood that a fossil will be discovered. You're
assuming both that each of the creatures you're comparing were equally likely
to fossilize and that the places where they were discovered were a
representative sample of the large area you're concerned with.
My term C:D is defined to include not just the relative likelihood of
fossils existing, but also of being found.
'That's because the original 1000 was not core data you were interested in,
only a population containing it. However, fossils identified as members of
the maniraptora have a likelihood considerably greater than 1% of being
The respondents were also genuine, though the screening instrument used tends
to have a 50% false positive rate according to a recent validation. The
problem is the small number of samples; there were simply not enough to allow
analysis of a population. Any statement beginning 'x% of' was impossible.
So, 171 (at the very least) Arctometatarsalia + Maniraptora have been found
after _Archaeopteryx_ and none before (if we discount the Segno J Jaw).
This is a lot more than I thought, and is going to give some strong
opposition to any hypothesis claiming any (Arctos/Mani's) occured before
Seems that you're beginning a statement '100% of' covering millions of years
and the entire earth from 171 samples classified into a very few types. If
this group existed in certain places at certain times and archae existed in a
certain place at a certain time and birds existed at certain places at certain
times and each have similarities, is this by itself enough to draw a