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  • Predicted vs. Found Relations

    Okay people, be nice here as the last thread was shut down:

    Predicted: 2nd -4th
    Paper trail: 4th cousin
    Total cMs: 81.39
    Largest block: 48.55 on chr 5

    Predicted: 2nd - 4th
    Paper trail: 3 x 5th C1R (3 cousinships at this level and all feeding in to same lineages and no closer relationships found)
    Total cMs : 57.64 on 2 blocks; 23.03 on chr 15 and 15.81 on chr 7

    Predicted: 3rd to 5th
    Paper trail: 5th but with possible other relations interacting
    Total cMs: 29.35
    Largest block: 17.75 on chr 12

    Predicted: 5th to remote
    Paper trail: 3rd1R
    Total Cms: 26.34
    Largest block: 8.77 on chr 6

    Predicted: 4th to remote
    Paper trail: 7th cousin (this person also 7th couisn to above 3rd1R cousin)
    Total cMs: 33.61
    Largest block: 12.01 on chr 11


    Predicted: 4th to remote
    Paper trail: 4th1R
    Total cMs: 37.76
    Largest block: 11.04 on chr 2

    Predicted: 5th to remote
    Paper trail: 5th
    Total cMs: 24.85
    Largest block: 10.91 on chr 5


    I think I have a few more I can add. Have to check.

    Linda

  • #2
    Originally posted by Peacock100 View Post
    Okay people, be nice here as the last thread was shut down:

    Predicted: 2nd -4th
    Paper trail: 4th cousin
    Total cMs: 81.39
    Largest block: 48.55 on chr 5

    Predicted: 2nd - 4th
    Paper trail: 3 x 5th C1R (3 cousinships at this level and all feeding in to same lineages and no closer relationships found)
    Total cMs : 57.64 on 2 blocks; 23.03 on chr 15 and 15.81 on chr 7

    Predicted: 3rd to 5th
    Paper trail: 5th but with possible other relations interacting
    Total cMs: 29.35
    Largest block: 17.75 on chr 12

    Predicted: 5th to remote
    Paper trail: 3rd1R
    Total Cms: 26.34
    Largest block: 8.77 on chr 6

    Predicted: 4th to remote
    Paper trail: 7th cousin (this person also 7th couisn to above 3rd1R cousin)
    Total cMs: 33.61
    Largest block: 12.01 on chr 11


    Predicted: 4th to remote
    Paper trail: 4th1R
    Total cMs: 37.76
    Largest block: 11.04 on chr 2

    Predicted: 5th to remote
    Paper trail: 5th
    Total cMs: 24.85
    Largest block: 10.91 on chr 5


    I think I have a few more I can add. Have to check.

    Linda
    Actually,

    Looking at these results, posted this way, the FTDNA alogorithm seems to be pretty much on coarse as to my FF matches, at least those I have identified.

    Linda

    Comment


    • #3
      Let's hope everyone can stay on topic. Here is my re-post.

      One confirmed with geneaology FF match:

      Predicted 4th
      Variance 3rd - 5th
      Actual 5th cousin 1x removed
      Total - 35.79 cM
      Longest - 12.86 cM

      Comment


      • #4
        2nd Cousin Matchings

        Family Case 1 (Permission given by family members to post)
        Family Member and Match: Lewis Ronald Lamar

        Juliette Turner (Grandmother)
        Shared cM: 345.91cM
        Longest Segment: 104.40
        Predicted: 2nd Cousin
        Actual: 2nd Cousin

        Stephen D. Handy Sr (Father)
        Shared cM: 170.49cM
        Longest Segment: 50.99
        Predicted: 2nd Cousin
        Actual: 2nd Cousin once removed

        Stephen D. Handy Jr (Myself)
        Shared cM 116.74cM
        Longest Segment: 50.99
        Predicted: 3rd Cousin
        Actual: 2nd Cousin twice removed

        Numbers weighed against concrete family knowledge and paper trail evidence.
        Attached Files
        Last edited by shandy4473; 2 March 2012, 07:11 PM.

        Comment


        • #5
          DIY Relationship Prediction

          Here is a chart you can use for Do It Yourself
          prediction of a relationship using the sum of all segments.
          Attached Files

          Comment


          • #6
            Originally posted by JSW View Post
            Here is a chart you can use for Do It Yourself
            prediction of a relationship using the sum of all segments.
            Very cool. It took me a few minutes to understand the plots, so this might be a little too much for some newbies especially if they are scientifically challenged. Anyway I'm curious where you got the data for your plots? I just see adapted from ISOGG.

            Comment


            • #7
              Data sources

              Most of it is from test on my family but there are other data that
              has been sent to me or posted in various places
              I had about 60 data points to build the blue and green lines

              Comment


              • #8
                It's a lot more complicated than that. I'd be careful on relying too heavily on a linear chart.

                Look at two people who have three children, John, Jack and Jill.

                John and Jack share 2950cM
                John and Jill share 2850cM
                Jack and Jill share 2900cM

                Because each sibling has a different admixture of his or her past ancestry via recombination, their children, first cousins, when compared to each other will only share a portion of the amount the sibling parents share. In the case of John and Jack, 2950cM.

                Those are moving reference points and they are relative.

                A grandchild of John and a grandchild of Jack will be second cousins. They will have some DNA in common with each other as second cousins. If you could compare the second cousin test with the test of John and Jack you would find the second cousins only share a part of what John and Jack shared to begin with. A third person, a grandchild of Jill will share differing amounts with John's grandchild and Jack's grandchild. This is because the reference points change depending on which two siblings are in common to the two cousins.

                The reason such a chart won't always work is because in the case I just outlined all descendants are sharing part maternal and part paternal alleles from the common ancestry and in each case different alleles are shared depending upon which two siblings are the origin of the reference pool. It's all relative as well. If another person is related by a different ancestor they may be phased when compared to the rest, it depends on where the common reference originales from.

                My point being in the test environment, the reference point is relative to the ancestry in common. In some cases the reference is phased to one parent and in some cases it is not. In the case of people descending from two common ancestors it is actually the children of the ancestors that are the first reference point in the alleles being shared and as they have children then those children inherit a portion of alleles, caused the shared amount to be smaller each generation on each branch going down.
                Last edited by mkdexter; 6 March 2012, 06:59 PM.

                Comment


                • #9
                  some fall out

                  Predicted: 2nd- 4th
                  Paper trail: 6th1R
                  Total cMs: 46.72
                  Largest block: 17.61

                  Comment


                  • #10
                    Originally posted by JSW View Post
                    Here is a chart you can use for Do It Yourself
                    prediction of a relationship using the sum of all segments.
                    Would have better luck with segment count and sum of segments for segments 5 cM or higher, at least out to 2nd cousin. Beyond 2nd, recombination too random to predicted within 1 degree of relationship with high level of confidence. Beyond 2nd, best to focus on ranges and expand far end of ranges provided by FF.

                    Comment


                    • #11
                      Back on Track - 1st Half Cousin Relationships

                      Family Case 2 (Permission given by family members to post actual names)
                      Family Member and Match: Dr Martin Hardeman PHD

                      Juliette Turner (Grandmother)
                      Shared cM: 410.60cM
                      Longest Segment: 62.40
                      Predicted: 2nd Cousin
                      Actual Relationship: 1st Half Cousin

                      Stephen D. Handy Sr (Father)
                      Shared cM: 331.78cM
                      Longest Segment: 54.20
                      Predicted: 2nd Cousin
                      Actual Relationship: 1st Half Cousin Once Removed

                      Stephen D. Handy Jr (Myself)
                      Shared cM 203.68cM
                      Longest Segment: 50.91
                      Predicted: 2nd Cousin
                      Actual Relationship: 1st Half Cousin Twice Removed

                      Example of confirmed 1st cousins that are half relatives. Variance of FTDNA's matching algorithm to actual relationships is expected and acceptable given it's ignorance to the actual half relationships.

                      Numbers weighed against concrete family knowledge and paper trail evidence.
                      Attached Files
                      Last edited by shandy4473; 7 March 2012, 01:09 PM.

                      Comment


                      • #12
                        Originally posted by mkdexter View Post
                        It's a lot more complicated than that. I'd be careful on relying too heavily on a linear chart.

                        Look at two people who have three children, John, Jack and Jill.

                        John and Jack share 2950cM
                        John and Jill share 2850cM
                        Jack and Jill share 2900cM

                        Because each sibling has a different admixture of his or her past ancestry via recombination, their children, first cousins, when compared to each other will only share a portion of the amount the sibling parents share. In the case of John and Jack, 2950cM.

                        Those are moving reference points and they are relative.

                        The reason such a chart won't always work is because in the case I just outlined all descendants are sharing part maternal and part paternal alleles from the common ancestry and in each case different alleles are shared depending upon which two siblings are the origin of the reference pool. It's all relative as well. If another person is related by a different ancestor they may be phased when compared to the rest, it depends on where the common reference originales from.
                        .
                        Great point. My brother and I certainly do not have each match listed the same way. Example, he has one match that FF says is a distant match and more than likely a 3rd to 5th cousin probable 4th and the same match for me is considered a remote 5th cousin.

                        Comment


                        • #13
                          DIY Chart

                          Matt is right when he wrote "The reason such a chart won't always work is because in the case I just outlined.........."

                          But that is not the only reason the chart won't always work
                          The processes we are random and thus there is always a "chance" that
                          the specific results we have are for out side of the normal range

                          The chart I posted should work "most of the time"
                          It also shows the wide range of possible relationships
                          when the result is less than 40 cM

                          Matt used an example of siblings in the 2900 cM range +/- a bit
                          But I have results that run from 2300 cM to 3000 cM for siblings
                          And as the generations go by these differences are multiplied

                          Comment


                          • #14
                            Siblings Matching others

                            RE "Great point. My brother and I certainly do not have each match listed the same way."

                            I would not expect siblings to match another person exactly - if at all.

                            Since each sibling got a different half of the DNA from the parent that
                            matched that third person. The results can be very different.

                            I match a 4th cousin and my brother has NO match at all with him
                            my match is 48 cM longest and 74 cM total.

                            As the relationship gets more distant and the number of segments drops
                            the odds that any segment makes it to the next generation is
                            always less than 50% - and if you are down to one segment
                            then it becomes all or nothing at that next generation.

                            Comment


                            • #15
                              DYI chart

                              RE "Would have better luck with segment count and sum of segments for segments 5 cM or higher, at least out to 2nd cousin. Beyond 2nd, recombination too random to predicted within 1 degree of relationship with high level of confidence. Beyond 2nd, best to focus on ranges and expand far end of ranges provided by FF. "

                              I did look at added complexity such as number of segments and length
                              of largest segment.
                              But none of those added enough discrimination to make it worth while
                              Others may be able to publish charts using more complicated data
                              and I welcome them.

                              Comment

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