Square root biased sampling

Square root biased sampling is a sampling method proposed by William H. Press, a computer scientist and computational biologist, for use in airport screenings. It is the mathematically optimal compromise between simple random sampling and strong profiling that most quickly finds a rare malfeasor, given fixed screening resources.^[1][2]

Using this method, if a group is ${\displaystyle n}$ times as likely as the average to be a security risk, then persons from that group will be ${\displaystyle {\sqrt {n}}}$ times as likely to undergo additional screening.^[1] For example, if someone from a profiled group is nine times more likely than the average person to be a security risk, then when using square root biased sampling, people from the profiled group would be screened three times more often than the average person.