Archiver > GENEALOGY-DNA > 2010-11 > 1289177427

From: "Tim Janzen" <>
Subject: Re: [DNA] "Relationship Range" Confidence Level
Date: Sun, 7 Nov 2010 16:50:27 -0800
In-Reply-To: <>

Dear Harold,
I believe that the "high confidence" prediction is very high
(approaching 100%) when predicting relationships for relatively close
relatives (first cousins and more closely related). The prediction level is
high for predicting 2nd cousins, but not as high as for predicting first
cousins. There is definitely overlap for results between 1st cousins once
removed and 2nd cousins and to a lesser extent there is overlap for results
between 1st cousins once removed and 1st cousins. The prediction level is
relatively low when you get out to the 3rd cousin and more distant level of
genealogical relationship.
I would suggest you review the chart I have at for background. If you
carefully review this chart, you will see that using 23andMe data (and also
Family Finder data since it is very similar) you can accurately predict the
genealogical relationship to the level of first cousin with a high degree of
accuracy if you use the total cMs of IBD segments as the primary data point
on which you interpret the results. Beyond the level of 1st cousin, things
are a little bit more unclear until you reach approximately the 3rd cousin
level of relationship, but you can generally be reasonably accurate in your
prediction of the genealogical relationship between the 1st and 3rd cousin
level of relationship. Once you get to the 3rd cousin and more distant
level of genealogical relationship, then things get much murkier. I
generally encourage people who have between 7 and 50 cMs IBD segments or 1-4
IBD segments in common to avoid making a prediction as to the precise
genealogical relationship based solely on the comparison of two people's
results. Instead simply begin looking for the genealogical relationship and
keep in mind that the relationship could be at the 5th or more distant
cousin level of relationship, particularly when you get down to only 1 or 2
IBD segments in common or only 10 or less cMs of IBD segments.
The following slides from a presentation on autosomal DNA I gave
earlier this year may also be of help. When the DNA results are somewhat
unclear as to the precise genealogical relationship, you may want to
consider testing more relatives to help refine the level of relationship.
The bottom line is that you need to think of the comparisons between any two
people as suggesting a range of possible genealogical relationships when the
relationship is more distant than the first cousin level of relationship.
Always view the DNA results in the light of your overall genealogical
research findings.


Tim Janzen

Ranges of total cMs of IBD segments based on family relationship

. Parent/child: 3539-3748 cMs

. 1st cousins: 548-1034 cMs

. 1st cousins once removed: 248-638 cMs

. 2nd cousins: 101-378 cMs

. 2nd cousins once removed: 43-191 cMs

. 3rd cousins: 43-ca 150 cMs

. 3rd cousins once removed: 11.5-99 cMs

. 4th and more distant cousins: 5-ca 50 cMs

Ranges of the number of shared IBD segments based on family relationship

. Parent/child: 23-29

. 1st cousins: 17-32

. 1st cousins once removed: 12-23

. 2nd cousins: 10-18

. 2nd cousins once removed: 4-12

. 3rd cousins: 2-6?

. 3rd cousins once removed: 1-4

. 4th and more distant cousins: 0-2

Ranges of percentage of genome in common per 23andMe's Relative Finder

. Parent/child: 47.54-53.24

. 1st cousins: 7.31-13.8

. 1st cousins once removed: 3.3-8.51

. 2nd cousins: 2.85-5.04

. 2nd cousins once removed: .57-2.54

. 3rd cousins: ca .3-2.0

. 3rd cousins once removed: .11-1.32

. 4th and more distant cousins: .07-.5

-----Original Message-----
[mailto:] On Behalf Of E. Harold Vannoy
Sent: Sunday, November 07, 2010 4:04 PM
Subject: [DNA] "Relationship Range" Confidence Level

Does anyone know what the confidence levels are for the "Relationship
Ranges" for FTDNA "Family Finder" and 23andMe "Relative Finder"? Are
they about the same? FTDNA says that Family Finder's Relationship Range
is a "high confidence" prediction of the possible relationships between
two people. Does "high confidence" mean 90% or 95% or what?

Any input on this would be appreciated.

Thanks in advance,

Harold Vannoy

This thread: