Perplexed in Peoria wrote:
> "Anon."  wrote
in message
> news:cbpfed$8kv$1{at}darwin.ediacara.org...
> 
>>Too much statistics - it simply isn't a distribution in the sense I
>>would use the term.  The only "frequency distribution"
(in the sense
>>that I would use the term) would be the tri-nomial distribution with
>>cell probabilities {p^2, 2p(1-p), (1-p)^2}.
> 
> 
> Bob, you might check your texts.  According to what I read, you have
> just described a binomial distribution (with n=2).  The corresponding
> trinomial distribution would have six cells:
> 
> ( p^2, q^2, r^2, 2pq, 2pr, 2qr) with the constraint that p+q+r=1.
> 
No, a binomial distribution has N events, with two possible outcomes per 
event (often called "success" and "failure", or if
p=0.5, H and T).  For 
H-W, we have three outcomes: two homozygotes and a heterozygote, and N 
is the size of the sample taken from the population.

The number of copies on one of the alleles in an individual is 
binomially distributed, but H-W is a statement of the proportions of the 
three genotypes in the population (this is not to say that the "alleles 
per individual" interpretation is incorrect, but just that it isn't used).

Bob

-- 
Bob O'Hara

Dept. of Mathematics and Statistics
P.O. Box 4 (Yliopistonkatu 5)
FIN-00014 University of Helsinki
Finland
Telephone: +358-9-191 23743
Mobile: +358 50 599 0540
Fax:  +358-9-191 22 779
WWW:  http://www.RNI.Helsinki.FI/~boh/
Journal of Negative Results - EEB: http://www.jnr-eeb.org
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