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Archiver > GENEALOGY-DNA > 2005-10 > 1130503403


From: "Ken Nordtvedt" <>
Subject: Re: [DNA] PubMed abstract: Gusmao study on Y-STR mutation rate
Date: Fri, 28 Oct 2005 06:43:23 -0600
References: <1c3.345b1bbf.30934a14@aol.com>


Ok, the formulas meant improbable.
----- Original Message -----
From: <>
To: <>
Sent: Friday, October 28, 2005 3:32 AM
Subject: Re: [DNA] PubMed abstract: Gusmao study on Y-STR mutation rate


>
> Ken wrote:
>> Just because someone's table does not show a probability for 9
>> mismatches
>> for 3rd cousins does not mean probability is zero.
>>
>> I don't understand this literalism contained in "our current model says
> ....
>> results are impossible"? How does something that may be improbable
>> become
>> impossible?
>
>
>
>
> Ken
>
> I don't seem to have your post on this topic. Was it onlist? No matter.
> If you create a binomial or Poisson distribution for P[x mismatches|y TEs
> *
> z markers] The P[9|6*37] will come out 0.0000. That's a zero
> probability
> and therefore impossible. Carry it out more places and eventually a 1
> will
> show up.
>
> On the MCRA Table 32/37 1-7 generations have no entries. The cumulative
> probability by 8 generations is 0.1% Technically yes, there is some
> probability, no matter how small for the 1-7. However, any elementary
> statistics course
> will teach you that for PRACTICAL purposes probabilities that low are the
> same thing as impossible.
>
> Hurst's results were apparently so "impossible" -- from a practical
> standpoint -- since "the probability was too low to take seriously (on
> the order of
> 1e-5)," that retesting was suggested (although I was unaware of this
> until
> now.) An excellent illustration of the difference between THEORETICAL
> "Probability" and OPERATIONAL "impossibility". So, ok Hurst was not 9
> mismatches in
> 3rd cousins after all.
>
> So let's try David Faux's dad and second cousin with 5 mismatches or Jerry
> Ivey's situation.
> David's dad and his second cousin have 5 mismatches MRCA 0.1
> probability of a common ancestor within 8 generations. 0.00004
> probabliity.
>
> I have a pair of participants with 3rd cousins with 2 mismatches
> (Prob=0.3)
> Not impossible but improbable. At the request of the participants I can
> give
> no more data than this.
>
> You can examine Jerry's case here:
> Jerry Ivey
> _archiver.rootsweb.com/th/read/GENEALOGY-DNA/2003-10/1066960038_
> (http://64.233.161.104/search?:archiver.rootsweb.com/th/read/GENEALOGY-DNA/2003
> -10/1066960038)
>
> Again, we are talking about the functionality at the margins here. And its
> utility for folks trying to estimate connections where the paper trail has
> not
> been found.
>
> Anne
>
>
>
> ==============================
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