Predicting Time to Common Ancestors 3

Analyzing the FTDNA TiP Calculator Results
Part 2
by Ed Ralston

Let’s assume you know from solid genealogical information, that your common ancestor does not occur within seven generations. So those first seven generations can be excluded from the calculations. In the TiP tool this can be set by changing the “did not share a common ancestor” to 7 generations. The resulting data and added incremental amounts are:

The first seven generations were excluded and the percentages adjusted. Note the highest odds for particular generations are in the first several. There is an 81.3% probability the common ancestor is in the 8 to 12 generation range and 60% in 8 to 10 generations.

The exclusion of the first seven generations changed the percentages, but the predicted range is about the same. In this model the results in the 8 to 9 generation range are 43.9%, 10 to 11 – 28.5%, 12 to 13 – 15.3%, 14 to 15 – 7.3%, and above 16 – 5.0%, as is shown in the following pie chart:

This shows the highest probability is in the 8 to 9 range. Again, those picking the 95% level would be selecting around 14 generations, but the above shows this is in one of the lowest probability ranges.

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