Square root biased sampling
Encyclopedia
Square root biased sampling is a sampling
method proposed by William H. Press
, a professor in the fields of computer sciences
and computational biology
, for use in airport screenings
as a mathematically efficient compromise between simple random sampling
and strong profiling
.
Using this method, if a group is times as likely than the average to be a security risk, then persons from that group will be times as likely to undergo additional screening. 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.
. It had also been developed independently by Ruben Abagyan, a professor at TSRI in La Jolla, California, for use in a different context.
Press later proposed the use of square root biased sampling for use by airport security, in a paper published in Proceedings of the National Academy of Sciences
. He argued that this method would be a more efficient use of the limited resources possessed for screening, as compared to the current practice, which can lead to screening the same persons frequently and repeatedly. Use of this method presupposes that those doing the screening have accurate statistical information on who is more likely to be a security risk, which is not necessarily the case.
Sampling
Sampling may refer to:*Sampling , converting a continuous signal into a discrete signal*Sampling , converting continuous colors into discrete color components*Sampling , re-using portions of sound recordings in a piece...
method proposed by William H. Press
William H. Press
William H. Press is an astrophysicist, theoretical physicist, and computational biologist. He is a member of the United States National Academy of Sciences, the American Academy of Arts and Sciences, and the Council on Foreign Relations. Other honors include the 1981 Helen B...
, a professor in the fields of computer sciences
Computer Sciences
Computer Sciences can refer to:*The general field of computer science*Computer Sciences Corporation, the Fortune 500 Information Technology company...
and computational biology
Computational biology
Computational biology involves the development and application of data-analytical and theoretical methods, mathematical modeling and computational simulation techniques to the study of biological, behavioral, and social systems...
, for use in airport screenings
Airport security
Airport security refers to the techniques and methods used in protecting airports and aircraft from crime.Large numbers of people pass through airports. This presents potential targets for terrorism and other forms of crime due to the number of people located in a particular location...
as a mathematically efficient compromise between simple random sampling
Simple random sample
In statistics, a simple random sample is a subset of individuals chosen from a larger set . Each individual is chosen randomly and entirely by chance, such that each individual has the same probability of being chosen at any stage during the sampling process, and each subset of k individuals has...
and strong profiling
Offender profiling
Offender profiling, also known as criminal profiling, is a behavioral and investigative tool that is intended to help investigators to profile unknown criminal subjects or offenders. Offender profiling is also known as criminal profiling, criminal personality profiling, criminological profiling,...
.
Using this method, if a group is times as likely than the average to be a security risk, then persons from that group will be times as likely to undergo additional screening. 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
Square root
In mathematics, a square root of a number x is a number r such that r2 = x, or, in other words, a number r whose square is x...
biased sampling, people from the profiled group would be screened three times more often than the average person.
Development
Press developed square root biased sampling as a way to sample long sequences of DNADNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
. It had also been developed independently by Ruben Abagyan, a professor at TSRI in La Jolla, California, for use in a different context.
Press later proposed the use of square root biased sampling for use by airport security, in a paper published in Proceedings of the National Academy of Sciences
Proceedings of the National Academy of Sciences
The Proceedings of the National Academy of Sciences of the United States of America, usually referred to as PNAS, is the official journal of the United States National Academy of Sciences...
. He argued that this method would be a more efficient use of the limited resources possessed for screening, as compared to the current practice, which can lead to screening the same persons frequently and repeatedly. Use of this method presupposes that those doing the screening have accurate statistical information on who is more likely to be a security risk, which is not necessarily the case.
See also
- Numerical RecipesNumerical RecipesNumerical Recipes is the generic title of a series of books on algorithms and numerical analysis by William H. Press, Saul Teukolsky, William Vetterling and Brian Flannery. In various editions, the books have been in print since 1986...
, a series of books on algorithmAlgorithmIn mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...
s and numerical analysisNumerical analysisNumerical analysis is the study of algorithms that use numerical approximation for the problems of mathematical analysis ....
coauthored by William Press.