The Polygraph and Lie Detection (2003) / Chapter Skim
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Appendix K: Combining Information Sources in Medical Diagnosis and Security Screening
Appendix K: Combining Information Sources in Medical Diagnosis and Security Screening
Pages 364-374
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From page 364... ...
In terms of the use of information, the problem is similar enough to that of security screening that much of the extensive literature on medical diagnosis may be consulted for insights relevant to security screening. In making judgments about whether an examinee is a security risk or has committed security violations, government security officials might take into account polygraph charts and at least five other types of information: 1.
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From page 365... ...
This appendix provides an overview of approaches used for combining information with statistical or other formal objective numerical algorithms, largely with reference to the medical diagnosis literature. These approaches, increasingly though inconsistently applied in clinical medical practice, contrast greatly with what we have seen in government security screening programs, in which polygraph and other information are combined essentially by clinical judgment, which can be considered as an informal, practitioner-specific algorithm incorporating hunches and rules of thumb.
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From page 366... ...
all variables thought to be potentially useful classifiers. The group prevalences and misclassification costs are typically estimated from other sources of information.
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From page 367... ...
In personnel security screening, one might consider the polygraph test, the background investigation for clearance, and various psychological tests administered periodically as the components of a parallel test: security risk is judged to be absent only if all the screens are negative for indications of security risk. Under the assumed independence among tests, the specificity (1false positive rate)
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From page 368... ...
The independent parallel testing argument suggests that polygraph testing might be useful in the security screening context even if it were not sufficiently valid by itself to be useful. A negative polygraph examination combined with other negative data might increase the certainty of a decision to grant or continue access to sensitive information.
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From page 369... ...
A serial test usually begins with relatively inexpensive and noninvasive measures and proceeds to more expensive and more invasive procedures as the accumulation of information makes the presence of the feature of interest increasingly likely. One can imagine a polygraph test as the first step in a personal security screening sequence, with more expensive background checks, detailed interrogations, and possibly levels of surveillance as later stages in the process.
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From page 370... ...
A plausible example is the possibility that the distribution of blood pressure readings obtained during the polygraph examination may differ dramatically for African American and white examiners (evidence making this hypothesis plausible is reported by Blascovich et al., 2001~. We have noted above that the statistical pattern recognition approaches require the training sample to be representative of the target population.
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From page 371... ...
The expected discrepancy is inversely related to the number of individuals in the development dataset relative to the number of candidate variables and is negligible only when the sample size is at least an order of magnitude higher than the number of candidate variables. Thus, pattern recognition approaches that analyze dozens or hundreds of variables will significantly overestimate their true validity unless they are developed on training samples with hundreds or thousands.
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From page 372... ...
2000 Artificial neural networks: Are they ready for use as clinical decision aids? Editorial.
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From page 373... ...
2000 Improved statistical classification methods in computerized psychiatric diagnosis. Medical Decision Making 20~1~:95-103.
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