GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2009-12 > 1260740710


From: "Ken Nordtvedt" <>
Subject: Re: [DNA] R-U152 and R-L21 on the European Continent
Date: Sun, 13 Dec 2009 14:45:10 -0700
References: <200912132124.nBDLOPPY003583@mail.rootsweb.com>


I don't know what statistical confidence intervals you are using, but they
seem much narrower than I believe should be the case.

For a simple TMRCA for two haplotypes, equivalent more or less to a very
deep interclade TMRCA, the one-sigma G estimate variance stated in
fractional units of the age, itself, is:

<dG^2> / G^2 = 1 / {2G Sum i [m(i)/(1+4m(i)G)]
with i being sum over markers.

The above is of course for markers assumed to be the simple text book
markers.

My rough estimate using your 24 slowest markers is that for 30,000 year
TMRCAs the one sigma dG/G is .36,
while for the extremely old age TMRCA only gets as good as .29

95 percent confidence interval is close to twice the one sigma values.

Ken








----- Original Message -----
From: "Tim Janzen" <>
To: <>
Sent: Sunday, December 13, 2009 2:23 PM
Subject: Re: [DNA] R-U152 and R-L21 on the European Continent


> 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.
>
>
> -------------------------------
> To unsubscribe from the list, please send an email to
> with the word 'unsubscribe' without the
> quotes in the subject and the body of the message
>



This thread: