A Laboratory Study of the Validity of the ZCT: An Executive Summary.
Final rept. Jan 88-Nov 90
DEPARTMENT OF DEFENSE POLYGRAPH INST FORT MCCLELLAN AL
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The validity of the Zone Comparison Test format was examined in an analog study conducted by the Department of Defense Polygraph Institute DoDPI. Forty subjects were tested by one of six psychophysiological detection of deception examiners PDDs after having been assigned to either the innocent group, or the group guilty of committing a mock theft of money. Standard field instrumentation and testing procedures were utilized, and the resulting examinations were evaluated by the original PDD examiner and three other examiners, all of whom were directed to apply either the DoDPI scoring rules or the rules used by the University of Utah. As a group, original examiner accuracy when using the DoDPI scoring rules was 70.0 for both the guilty and the innocent subjects, but was 73.7 and 77.8, respectively, when the inconclusive decisions were eliminated from the analyses. The numerical scores of the examiners, having been correlated with each other and with the guiltinnocence criterion, ranged from .84 to .90. Three of the four validity coefficients achieved statistical significance. In short, the ZCT format accuracy was lower in this study than in other laboratory studies. A list of possible factors contributing to these findings was provided and the author specifically noted that this study accounted for only 18.5 of the criterion variance, whereas, other studies have typically accounted for 60.0 - 70.0 of the variance.
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