HFA yDNA Project

Math terms used in this web site

What are Minimum, Mode, Median, Mean, and Maximum?

• Minimum The minimum is the smallest value present for this marker among all of the participants in the group being compared.  A separate minimum is calculated for each grouping within a project.
• Mode The mode is the most common result for this marker among the participants in the group being compared.  The mode value is calculated separately for each grouping within a project.  The mode value is also what is used when computing the genetic distance displayed through the colors in the chart.
• Median The median is the middle value present for this marker when the values are arranged in order from smallest to largest.  This is not necessarily the same as the average; for example, if you have the results 10, 16, 17, 17, 17, then the median is a 17 because when the numbers are listed in order from smallest to largest the middle one in the list is a 17.  A separate median is determined for each grouping within a project.
• Mean The mean is the average of the values participants have for this marker within the group being compared.  The mean is rounded up or down to the nearest whole number.  A separate mean is calculated for each grouping within a project.
• Maximum The maximum is the largest value present for this marker among all of the participants in the group being compared.  A separate maximum is calculated for each grouping within a project.

Understanding that marker matches/mismatches need to be understood statistically.
Assume we gathered a group that consists of all of the male decendants of a common ancestor who lived 8 generations ago. Assume that there were 500 of these male descendants. Forget how we could know that, just accept it for now. If we measured the standard panel of 37 yDNA markers for all of them and compared it against those same markers from a sample that we had of that common ancestor, this is what we would likely find:

The majority of participants would have the same markers as their ancestor. Many, but fewer would have 36 of the 37 match. Many, but even fewer, would match on 35 of 37 markers. The number of participants with even more mismatches will decrease quickly. We might even find a participant who mismatched by six or eight markers. We might find that 60% of the participants had perfect matches; that 80% had 0 or 1 mismatch; that 95% had 0,1, or 2 mismatches; that 98.5% had 0, 1, 2, or 3 mismatches; that 99.99% had 0, 1, 2, 3, or 4 mismatches. But there might be one participant who had 8 mismatches. His numbers would be called an "outlier". Typically, we would say that 6 or more mismatches indicate that participants don't share a common ancestor. However, remember the possibility of outliers, when you are comparing mismatches of 6-10.