could be rated on their cost in relation to the number of undetected spies (because of deterrence, this is slightly different from the cost per detected spy). To get to a cost-benefit analysis, one would need to put a dollar value on the cost of each undetected spy. Indirect effects of the program are also included in a thorough analysis. These would include the effects of detected spies on deterrence, the effects of false positives on morale and on the quality of scientific personnel that work in an agency, and the effects on other parts of the security system (for example, placing too much reliance on polygraph screening may result in loosening of ordinary security precautions, thus increasing the chances that a spy who is cleared by a polygraph examination will succeed in stealing secrets).
Most of the uncertainty in calculation and evaluation relates to modeling assumptions and subjective judgments rather than statistical noise. Also, policy makers typically are looking for choices that remain good even if conditions or goals change. For these reasons, analysts typically use sensitivity analysis to examine how choices and conclusions are affected by varying the subjective assumptions and parameter estimates over a reasonable range, rather than attempting to compute confidence intervals or make probabilistic statements about the best choice.
From this brief discussion it should be evident that there would be considerable difficulties involved in any quantitative policy analysis of the use of polygraph in periodic or aperiodic screening. An argument for conducting such an analysis despite the difficulties is that it may lead to better decision making than alternative strategies for making choices. For instance, leaving the choice to specialists may lead to inertia in maintaining policies that are no longer appropriate to changed conditions. Also, professionals have been noted to emphasize service to their clients rather than to society as a whole and may come to have undue faith in what they do (Fischhoff et al., 1981).
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