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From: "Jim Huffaker" <>
Subject: [DNA] Test Variability
Date: Thu, 1 Aug 2002 16:11:27 -0400
References: <7c.2bc85abf.2a7ad9fc@aol.com> <04ad01c23989$9cad48a0$a6f2153f@com>


I am trying to figure out what my group of Y-Chromosome results mean. HELP.

My brother and I were one count different at Y-GATA-A10. Thirteen for me, 14
for him. All the other loci counts were identical. The testing company just
remarked that it was unusual for brothers to not have identical counts at
all loci. My background is Analytical Chemistry and had my laboratory
produced "unusual" results, we would likely re-do the test over and again.
(And maybe they did). But the point is, given the paucity of data, it looks
to me as if test variance might as well be assigned to the results. In my
career we did not allow a cause to be un-assignable i.e. "Unusual". There
was a cause, else a random event or error and the result reported with a
range.

Getting to the point here, what is the reproducibility of the test method(s)
from which counts are determined? What range of values result from counts?
What is the 95% confidence interval of the range? These seem important
questions to me because the test results also conclude a common ancestor for
another participant and I and he and I had one count difference at DYS 390
and two count difference at DYS 392, from which it was concluded our common
ancetor lived in 1690 about. By what philosophy do we dismiss a one count
difference between my brother and I as insignificant, and the other case
significant?

Granted this is not my science, but I did learn a lot about test
variability, reproducibility, various kinds of errors and assignable causes
related to chemical analysis, surely this analysis has the same problems and
solutions. Grateful for explanations or assigned reading.


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