254 Forensic Laboratory Management: Applying Business Principles
In 1992 Bruce Weir suggested that we could use this approach to
determine a minimum allele frequency for alleles we did not see when
sampling for the databases, where alpha (α) is the signicance level, which
we typically set to 0.05 or 5%, and 2N where N is the number of individu-
als we have sampled, and 2N is the number of copies of the gene observed.
So, for example, let’s say we have looked at 200 people, or 400 copies of
a particular locus. We have never seen a particular allele (maybe an o-
ladder variant) but it turns up in a case. It is not present in our databases
so we apply this formula. Doing so, we can calculate the 95% upper con-
dence level of that allele frequen ...