Independence tests for VNTR alleles defined as quantile bins.

VNTR fragment lengths in three databases maintained by the FBI for forensic purposes were partitioned into quantile bins, and tests for independence of the two bins at each of six loci were conducted. Whether independence was declared depended on the number of quantiles used. For a large number of quantile bins, equal to the number of fixed bins used by the FBI, 10 of 18 likelihood-ratio tests showed significant departures from independence when all genotypes were considered, and this changed to 7 of 18 when only heterozygotes were tested. This is in contrast to likelihood-ratio tests on fixed bins, when there were five significant departures over all genotypes and two departures for heterozygotes.