YDNA Roger

What does "modal" mean?

There are several characteristic values of a set of sample values commonly used to describe, simplistically, the set as a whole. The most common is the mean, or average value. A second common one is the peak value, and a third is the mode. The mode is that value which occurs most often. It usually comes to the fore when the sample values in the set must be integers, and tend to be close to a central value, as is the case with yDNA marker values. Let's consider five possible sets of marker values.

Marker set Marker values Mean Mode
1 29, 29, 29, 29, 30 29.17 29
2 18, 19, 19, 19 18.75 19
3 12, 11, 12 11.67 12
4 15, 16, 16 15.67 16
5 16, 17 16.5 ?

In the last case the mode is indeterminate. We would have to wait for the data set to grow larger.

"Modal" means "of or pertaining to the mode." Genetic genealogists like to use the word "modal" to describe certain meaningful sets of YDNA marker values; for instance, haplogroups—"Modal R1b1b2" is the set of marker values which define haplogroup R1b1b2. There was a person who lived long ago, the ancestor of all the R1b1b2's, who had YDNA described by these marker values. And in our case "Modal Roger1" is our best guess for the set of marker values which would result from testing Roger1's YDNA, were it possible to test Roger1 today.