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Multiple-Issue Screening
Polygraph screening is a method for testing over more than one topic. It is commonly used in applicant screening. The test questions cover different topics, though sometimes there is a degree of overlap among relevant questions. For example, when four questions are used in a screening examination, the questions might be: Did you falsify your job application; Have you ever used illegal drugs on the job; Have you ever committed a felony, and; Did you ever steal anything from a previous employer?
Most research points to an accuracy of a screening test at about 70-80%. This may be a high estimate when more than four questions are covered, if the relevant questions are more ambiguous, or the relevant questions are presented fewer than three times during testing. This accuracy is greatly improved when the relevant questions are highly focused, there are fewer than four relevant questions, or if the examiner uses the "successive hurdles approach" in screening.
In the successive hurdles approach, subsequent testing is given to those applicants who react to a question in the screening test. The subsequent test would be tightly focused on the relevant question that caused the reaction on the screening test, and use a polygraph technique more closely approximating those used in single-issue testing. Only examinees failing the second test would be called deceptive. This multiple-step approach significantly boosts accuracy, ensuring that those who react on the screening test for reasons other than deception are differentiated from those who truly were lying.
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