TiP: a poor tool

Actually, it's not really the Tool that is a problem - but the interpretation people make.  (and there are no instructions on the TiP pages)   I regularly see folks with a yDNA test who are completely misusing and misunderstanding the FTDNA TiP tool.  If I had my choice, only Project Administrators could access TiP info (which would not prevent mis-use - but it would reduce i).  That may surprise you - so here's why I say that:

There is NO BASIS for talking about needing a certain % or number of generations when using the TiP comparison tool. 

This Tool is a statistical analysis for assessing the probabilities on large numbers of events.  When applied to a single situation, it is still accurate - but really VERY disappointing and not very useful or satisfying once you understand what it is saying.  It is ONLY valid if you appropriately interpret the information. 

The appropriate interpretation is that you use the entire range of possibilities.  In the example below, any separation from 1 generation to more than 16 generations can be the number of generations that separate me from Dale with our 65/67 match and still be consistent with the TiP report.  (Dale and I guess that our paper trails will connect in 7-9 generations if we ever find the paper trail connection)

When you are told that at 2 generations the percentage is 16.74% (my comparison with Dale at 67 markers - a GD=2), this means that 1674 of 10,000 men will share a most recent common ancestor with their match at 2 generations or less.  (For 10,000 random men who have a known connecting paper trail with their match and are GD=2 at 67 markers)

When you are told that at 4 generations the percentage is 46.67%, this means that 4667 of 10,000 men will share a most recent common ancestor with their match at 4 generations or less.  (For 10,000 random men who have a known connecting paper trail with their match and are GD=2 at 67 markers)

You ARE NOT looking for the level above 50% or above 90% and men with a level below some threshhold (say 25% should not be rejected as your relevant matches. You are also not correct in simply stating that the number of generations correlating to 50% or to 90% is the specific separation you have with your match.  (it might be true - but so are ALL of the other possibilities

More thoughts about Matches and their interpretation:

  1. Always (and only) compare your match with a man at the highest level that you are both tested.  (Ex: if you are tested to 67 and he is at 37 - compare at 37 markers.  The other comparisons at 25 and 12 markers are irrelevant (except in obscure situations)
  2. Accept that the yDNA matches listed by FTDNA are nearly always your genetic kin in the genealogical era -

    1.  If they are at 67 or 111 markers
    2. Are most likely your genetic kin when they are at 37 markers
    3. Are sometimes your genetic kin when they are at 25 or 12 markers
  3. Assume that PROBABLY, BUT NOT  CERTAINLY, your matches with fewer mutations are your closer kin.  For a discussion, read my Blog entry "Don't Count Mutations" at http://www.worldfamilies.net/blog/16609
  4. Realize that the values presented in the TiP estimate tables are a by-product of the calculations used to prepare the table and not a useful precision.  As example:

    1. "16.74" is much more appropriately viewed as "15-20%"
    2. There is no useful difference in 97.17%, 98.82% and 99.52% - think of all of them as "nearly everyone".- and that a very few will be more distantly related
  5. When in doubt, ask your administrator - or read our interpretation guide in "DNA the Smart Way" at   www.worldfamilies.net/smart

Terry

Updated 9-24-14