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Prability that my tree is 99.999% right?

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  • Prability that my tree is 99.999% right?

    Now well engrossed in the old family tree I was thinking about all the useful advice and suggested information sources I had received (often from friends here).

    So far my tree goes back to pre 1850 for all four major lines (the grandparents) and I’m 99.9% happy all are correct (and that based on just two marriage certs.). But when going sideways (into parts of the tree I didn’t previously know existed) or prior to say 1837 the confidence factor goes down.

    Sometimes of course you get lucky and get circular references. My great grandma has a daughter. The daughter goes through two marriages. The mother is already linked to two other siblings. Many years later the great grandma with one sibling in tow moves in with her daughter. Without boring you with all the details I have two distinct trails which go their separate ways and then reunite at a later date. The chance of this not being great grandma is now very slim.

    Well I was thinking, being that way inclined, of creating a formula to calculate confidence based on quality of data, number of data items, number of sources, quality of reference, independence of source (a lie maintained becomes fact), etc.

    What really got me thinking along these lines, and I don’t want or intend to be critical here, was some of the crazy connections ancestry offered for members of my tree. Now generally they are useful but at this simple level I feel they could be a bit smarter. (I’m in IT development by the way so I know how difficult developing clever software using what is known as ‘fuzzy logic’ is. And IMHO Ancestry as an example of a website is very slick).

    But before I get started I wondered if anyone had seen any research into this aspect of our hobby? Any references might save me reinventing the wheel.

    Cheers Nigel

    p.s. I know the detection is most of the fun and I don’t aim to look to automate that. I just am interested in generating probability of accuracy. For example an algorithm might examine a tree documented with sources and identify weaknesses that warrant further verification.

    Cheers Nigel
    Last edited by nigele2; 29-03-09, 13:44.

  • #2
    I know just what you mean Nigel! I was looking at a tree on Ancestry yesterday - supposedly of my family. It was like a fairy story! It would have been very useful if they had put onto the tree how likely or unlikely they thought the facts were. I don't think a lot of people think about it at all!

    Personally I couldn't be getting my head round a mathematical probability. When I enter something on my tree (on my computer) I put the source for each piece of info. If it is just based on censuses I can see that it is not as reliable as having a certificate. If it is based on the IGI it is not as reliable as seeing the actual Parish Records.

    If I get several sources for one fact (eg certificate, census match up, parish records, wills) then the chances are I'm 99% right.

    So you can see that I know by looking at my sources how likely it is. An inexperienced researcher might not pick up on those subtle points though!

    Anne

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    • #3
      Nigele2

      The Society of Genealogists suggests that three peices of evidence are required for each "fact", one at least of which must be from a primary source.

      Primary sources are: Certificates, (from local Register Offices) Wills, Parish records (originals) and various other items.

      A "FACT" would be that you knew your grandfather, Joe Bloggs, very well. This "FACT" although primary evidence, does not prove that Joe Bloggs was born Joe Bloggs, nor does it prove that he was your biological grandfather, it just proves the man existed, because you knew him. Everything about him needs to be proved.


      Any transcribed material is secondary evidence and is not proof of anything, as it stands, but can help to confirm facts.

      The more evidence you can collect from various sources, the more likely your tree is an accurate representation of the truth. The more evidence you can display from primary sources, the better.

      Many tree programmes have a facility for entering the probability of your sources and you can enter them as primary or secondary.

      Finally, remember the chain is only as strong as the weakest link - one mistake and the whole tree is rubbish!

      OC

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      • #4
        Maybe I should say my focus is the connection between two people. The fact that both existed is not normally in dispute. They could be the same person, they could be related (not only in the family sense), and they might be two distinct unconnected entities (beyond for example having the same surname).

        I guess a good example is William Shakespeare. World famous. Few people dispute such a named man was born and lived in S-u-A. But many doubt that that man wrote any plays or sonnets. While documents might make a connection logic says it is extremely unlikely. The playwright(s) might have used a pseudonym which was the same as the others name. And of course it could even have been an early example of identity theft. And of course as unlikely as it is the school taught version (in my day) maybe true.

        But each solution has a calculable probability - even if that probability has some probability of being incorrect.

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        • #5
          my grandmother always taught me to have three things to prove evidence.
          funny, coz sometimes she didn't have more than one.

          as for shakespeare, isn't it a bit funny to think so many people could be just like each other? i wonder what elizabeth I would have said!!

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          • #6
            Originally posted by kylejustin View Post
            my grandmother always taught me to have three things to prove evidence. funny, coz sometimes she didn't have more than one.
            I like that "do what I say and not what I do" :D.

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            • #7
              lol, it has grandma written all over it!!

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              • #8
                My 2 x GGF, James Holden is a pain.

                He first appears at the age of 37, marrying for the second time as a widower. I have him in 61,71 and 81. He then vanishes again, till he turns up dead in 1898, miles out of area.

                So, I can prove he lived and I am reasonably certain I have him accurately mapped from his second marriage forward. The two things he is consistent about is his age and his birthplace.

                Many many years of research have turned up a very likely candidate for his birth - right time, right place. He was born illegitimate, in the workhouse. I know who his biological father is and have traced that family forward and backwards. I know who his mother was and have traced her family backwards. I am 95% certain this James Holden is MY James Holden.

                But I cannot prove it! So, would you consider this part of my tree to be 95% accurate - or not accurate at all? It could be either, there is no inbetween, it is either right or it is wrong.

                OC

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                • #9
                  i would think it was true if i found a will that mentioned it.

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                  • #10
                    Originally posted by Olde Crone Holden View Post
                    it is either right or it is wrong.

                    OC
                    and that is why it is a probability. I guess there are in reality very few definates in life (and certainly in death :D). All we can say is that most likely .....

                    The thing I have found most interesting is the lives these people lived, the occupations, thinking how they lived 13 to a house. I would like to think I have done all I can to be accurate but beyond that it doesn't matter.

                    I thought I had found my great x2 grandma but she turns out to be the servant. When my great x 2 grandma died she replaced her and carried on producing (but my great grandpa was child of the original). But I'm now more fascinated by her 'Ann Cole' than the real blood line.


                    As for my research and possible algorithm I would like it to point me to the weak links so that I can focus there. Sometimes I think I have proven my case but cold analysis highlights a floor in my thinking.

                    Finally the probability of me spelling probability correctly in the thread title is 0% - I'm 100% certain of that
                    Last edited by nigele2; 29-03-09, 15:05.

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                    • #11
                      I totally agree with the need to cross reference everything, buy certificates etc. However, there are times when I see names or some documentation and can sometimes get a sixth sense whether its relevant to my tree. The problem is proving it. I do try and make notes regarding any data I am not totally sure about. Am I being a bit naughty adding data and then proving(or disproving) at a later date.
                      Last edited by Sherbertrose; 29-03-09, 15:47.

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                      • #12
                        Oh dear Nigel ..... my head's buzzing.

                        Hope my children don't read this thread, they'll be wanting my husband to prove he's their father .... lol.

                        Seriously ..... it is suppose to be pleasurable ... and everybody can only do their research to the best of their ability. That is what I've written at the end of my book ... and if family members want to carry on after I've gone, they're quite welcome to correct any mistakes..... I've done my bit 'to the best of my ability'

                        Jean
                        Jean....the mist is starting to clear

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                        • #13
                          Originally posted by Jean and Tonic View Post
                          Hope my children don't read this thread, they'll be wanting my husband to prove he's their father .... lol.
                          Jean
                          I'm 100% sure it is not me ;)

                          just for fun:

                          Here's a thought: there are 3 possible grandmas: Jane Smith b 1801, Jane Smith b1802 and Jane Smith b 1803. You have a gut feel for Jane Smith 1801 for no rhythm or reason. Then it is proved that Jane Smith 1803 is not your grandma. Is Jane Smith 1802 more or less likely than Jane Smith 1801 to be the true grandma?

                          Problem is Jean I find these things fun - must go, the men in white coats have arrived

                          Comment


                          • #14
                            imagine this: mary wyatt born marylebone 1801, 1802, 1803, 1805, 1806, 1807, and 1808. plus a maria in 1806.

                            which one to go for when you know nothing of her family?

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                            • #15
                              Sherbertrose

                              Yes, I often work on gut instinct and it usually turns out to be correct - but not always, and that's the sticking point.

                              Nigele2

                              Two Janes, 1801 and 1802 - the probability is 50%, OF THOSE TWO WOMEN. The problem - yours and mine - is that the "last man standing" may not be yours, even after you have eliminated everyone else because you may not have found yet another Jane Smith.

                              My James Holden is the last man standing (out of HUNDREDS!) - but I am very mindful that he may have been born somewhere else entirely - Timbuctoo for all I know. I am also mindful that he may have been missed off a baptism register, or not baptised at all, or even have been born with another name.

                              OC

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                              • #16
                                A very interesting topic. But underlying all the talk about facts, proof and probability is the certainty that the only person who really knows who a child's father is is the mother, and sometimes even she doesn't know, or will not admit it.

                                After the event, 100% certainty of parentage is impossible.

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                                • #17
                                  dont worry oc, even if you dont find him in this our lifetime, there's always next century:D

                                  Comment


                                  • #18
                                    hughar

                                    I think what you are talking about is slightly different.

                                    I take the attitude that if everything LOOKS LIKE Joe Bloggs is the son of Arthur and Minnie Bloggs - including the birth cert AND there is no evidence that he may have been a cuckoo, then we have to accept that.

                                    If we start worrying whether Joe Bloggs MIGHT have been a cuckoo, then family history is not the right hobby for us - perhaps pure mathematics instead, lol!

                                    Family history is a game with rules and as long as you stick to the rules (i.e. PROOF on paper) and don't ignore any doubts you might have, then you have played the game according to the rules and that is all any of us can hope for.

                                    OC

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                                    • #19
                                      I use FTM 2006 and where I have a good candidate I put them on my tree with a question mark after their name and enter the details (including for and against) in their individual notes section.

                                      In this way I do not lose sight of them but am reminded (as are other people viewing the tree) that the individual named is only a possibility. My ambition is to get rid of all the question marks in my tree but I know in my heart that this is highly unlikely.

                                      Comment


                                      • #20
                                        Originally posted by nigele2 View Post
                                        I'm 100% sure it is not me ;)

                                        just for fun:

                                        Here's a thought: there are 3 possible grandmas: Jane Smith b 1801, Jane Smith b1802 and Jane Smith b 1803. You have a gut feel for Jane Smith 1801 for no rhythm or reason. Then it is proved that Jane Smith 1803 is not your grandma. Is Jane Smith 1802 more or less likely than Jane Smith 1801 to be the true grandma?

                                        Problem is Jean I find these things fun - must go, the men in white coats have arrived

                                        Only joking ...I find them fun as well Nigel, I love puzzles anyway.

                                        Like OC ... I have one that I don't think I'll ever prove, even after finding leases, parish documents and other papers, so I've bowed down to the experience of someone who has been researching the family for many years and written books. That doesn't mean he's right but I either stop where I am or take it as possibly true. At the end of the day .. it's in the 1700s so I can't see my family being that bothered anyway. Like you.. I prefer to find out more about how and where my families lived in the 1800s

                                        Jean
                                        Jean....the mist is starting to clear

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