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Archiver > GENEALOGY-DNA > 2009-12 > 1260739439


From: "Tim Janzen" <>
Subject: Re: [DNA] R-U152 and R-L21 on the European Continent
Date: Sun, 13 Dec 2009 13:23:59 -0800
In-Reply-To: <009d01ca7c34$3bfc1400$6400a8c0@Ken1>


Dear Ken,
I certainly do take confidence intervals seriously. The confidence
levels aren't particularly large for the 24 slow marker option, even for old
nodes. As I said in a recent message, I would rather accept a wider
confidence interval and know that there is a reasonable probability that my
interclade TMRCA estimates are accurate than to include a lot of fast
mutating markers that are clearly skewing the TMRCA estimates to be lower
and thus clearly creating TMRCA estimates that must certainly be incorrect.
It is obviously more important to have TMRCA estimates that are accurate
than to have narrow confidence intervals. Note that in one of my recent
messages I gave a TMRCA estimate for the node for haplogroups A and B using
50 markers. The 95% confidence interval was relatively narrow (3070 years),
but the TRMCA (35,245 years) was clearly wrong and we all know that even
after adding 3070 years to the estimate, that you are still far lower than
the true TMRCA. In contrast, the 95% confidence interval for the 24 slow
markers was 22,000 years. As you may recall, the TMRCA estimate was 77,576
years. The true TMRCA for node for haplogroups A and B could be older that
100,000 years, but it is almost certainly not less than 55,000 years.
Another important point I have mentioned before and I think it bears
repeating again: The true TMRCA for each node on the Y tree is hemmed in by
the nodes above and below that particular node on the Y tree. If you look
at the TRMCA estimates for various subhaplogroups in R1b that I posted in
this message
http://archiver.rootsweb.ancestry.com/th/read/GENEALOGY-DNA/2009-07/12468584
73 in July, you will see that the estimates fall into an even progression
from younger to older as you move up the Y SNP tree even for the 24 slow
marker option, which I referred to in this message as being the "new
version".
Sincerely,
Tim

-----Original Message-----
From:
[mailto:] On Behalf Of Ken Nordtvedt
Sent: Sunday, December 13, 2009 12:38 PM
To:
Subject: Re: [DNA] R-U152 and R-L21 on the European Continent


----- Original Message -----
From: "Tim Janzen" <>

I can live
> with higher confidence intervals if the results suggest that my TMRCA
> estimates are likely to close to the true TMRCA.

If you take statistical confidence intervals seriously, and they are huge,
you don't know if your estimates are close to the actual TMRCA.


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