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Archiver > GENEALOGY-DNA > 2003-11 > 1069471893


From: Charles <>
Subject: Re: [DNA] Genetic Distance calculation -- which method is best
Date: Fri, 21 Nov 2003 22:31:39 -0500
References: <3FBE77A0.2050808@kerchner.com> <REME20031121211843@alum.mit.edu>
In-Reply-To: <REME20031121211843@alum.mit.edu>


John,

I, nor anyone else in this thread that I know of is saying that the two
people that were discussed the other day who were 19/25 markers relative
to each other, with differences at markers of 2, 2, 2, 1, 1, 1, are
closely related. What I was questioning when I asked you my question was
which method of calculating and expressing the Genetic Distance (GD) in
such a case is the correct or better method.

FamilyTreeDNA's method says for the case in point the other day: GD =
2+2+2+1+1+1 = 9

And you advocate the sum of the squares of the differences which for the
case in point the other day: GD = (2*2)+(2*2)+(2*2)+(1*1)+(1*1)+(1*1) = 15

If you strongly believe your approach is more valid I really encourage
you to continue the dialog with Bruce Walsh and advocate your approach
be adopted by FamilyTreeDNA via Bruce Walsh.

I think it would be helpful to newbies and old-timers alike to get this
issue resolved, for consistencies sake. Hopefully you and Bruce Walsh
will continue this debate via private emails and if you sway the
argument to your point of view, then hopefully FamilyTreeDNA would
changed their GD calculation algorithm in their website page for surname
project coordinators to use your method. What we need in this new
industry, for newbies and old-timers alike, is consistency. And this GD
calculation method is one area which still seems to be in a state of flux.

Charles


wrote:

> On the other hand,
> let's look at the case that we were talking about just yesterday: the
> match was 19/25, and the differences were 2, 2, 2, 1, 1, and 1. Under
> the circumstances, it would be absurd to assume the two individuals
> are closely related. The sum of the squares is the only reasonable
> approximation to the genetic distance in this case.
>
> John Chandler



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