Re: False negatives in Family Finder test #dna
Sarah L Meyer
The answer to the probability question is in part given in the FAQ's (What
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is the probability that my relative and I share enough DNA for Family Finder to detect? The FAQ's have chance of detection 2nd cousin or closer >.99 3rd cousins >.90 4th cousins >.5 5th cousin >.1 6th and more distant <.02 I had a second cousin once removed, test as a distant cousin, so my interpretation is that that these percentages are the chances of detecting the correct relationship (and not just any relationship). Unless FTDNA is saying that those probabilities are the probability of detection at any level I have to assume that they are at the stated level. So the probability of being missed is 1 the probability of being detected. So for second cousins or closer there is less than a 1% chance of being missed and for third cousins is <10%, fourth cousins <50 percent etc. (BTW Gedmatch had him at 3.5 generations to MRCA). Ignoring the less than or greater than signs (since they did not give us more places past the decimal), in my case without considering the possibility of a second cousin being considered a 3rd cousin etc with TWO people being missed, the chances of missing both were (less than) .0001 or 1 in 10,000, which is why if there was no error in the DNA processing, I was going to look for "the milkman". And if I were to take into consideration  a match at *any* level, the chances would have been much smaller. In this case, I think we need to look at this as if they were second cousins (they are actually closer) and the chances that they did not find them as second cousins is less than 1%, the chance that they will be found as second cousins or third cousins (but not second) is .99+.01*.9=.999 so the chance of missing them as both a second cousin and a third cousin would be .001 etc. A calculations gives that the probability of detection at any level up through 5th cousins is .99955 which would say the probability assuming that each of those > signs was an equal sign and that the match did not occur at any level is .00045. This does not even take into account the probability of a 6th or greater cousin match. That is why at this level of known relationship, I suggested that GEDMATCH.com be used to see if the location of the error could be determined. Sarah L M Christiansen Georgetown TX 78633
From: Judy Simon <heyjude0701@gmail.com>

