Archiver > GENEALOGY-DNA > 2010-03 > 1269796103

From: David Faux <>
Subject: Re: [DNA] 23andme cousin results
Date: Sun, 28 Mar 2010 10:12:59 -0700
References: <><><><><00d901cace95$a4b8bda0$5e82af48@Ken1>
In-Reply-To: <00d901cace95$a4b8bda0$5e82af48@Ken1>

No, but I have never seen any sort of document of this nature with
confidence intervals. The FTDNA charts give a good idea of expected values
which means there should be some sharing to the third cousin level and then
drop off precipitously - even past the point of sharing shown by Relative
Finder with 23andMe (about 0.08%). In a way 23andMe does include confidence
intervals in that they call a match as say 4th to 7th cousin. Also, as I
said, unless I misunderstand some fundamental genetic principles, there
should be more sharing in direct male lines than direct female lines as a
function of the differential rates of recombination in males and females -
but this is not factored into any calculation I have seen. So what we see
are general guidelines that "work" increasingly "better" with closer
relationships. There will of course even be confidence intervals that apply
to say inheritance from each great great grandparent - in theory we
receive 6.25% from each.

With the X - chromosome of a male, he may have received a zero percent
contribution via his maternal grandmother, a 100% contribution or anything
in between (via recombintation with his paternal grandfather's X in a
meiosis from his own mother). That is quite the confidence interval in so
short a time.

David K. Faux.

On Sun, Mar 28, 2010 at 9:42 AM, Ken Nordtvedt <>wrote:

> ----- Original Message -----
> From: "David Faux" <>
> > The two charts provided by FTDNA on the FAQ page for their Family Finder
> > are
> > extremely helpful in understanding complexities such as how much a thrid
> > cousin twice removed "should" share with you. They are found here:
> >
> By any chance did FTDNA include the statistical confidence intervals, or
> better yet the actual distribution of relationships relative probabilities,
> for the various levels of sharing?
> That would be useful information.
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