FIGURE H-3 Accuracy index (A) values calculated from 52 datasets from laboratory studies.

NOTE: Vertical lines are the length of one standard error; they extend downward from the accuracy index value for convenience of presentation.

have arisen by chance from studies with particularly small sample sizes, but in fact these groups of studies have sample sizes comparable to the larger collection. It is also interesting to note that values of A have not been increasing over time, as they might be expected to do if, as some members of the polygraph community have suggested to the committee, older studies underestimate the accuracy of current polygraph testing due to recent improvements in technique. The 6 datasets with the lowest A values were all reported in the 1990s, while the 7 datasets with highest A values were reported between 1968 and 1989, and none of the 9 datasets with A exceeding 0.95 were among the 22 datasets reported after 1992. Looked at another way, the median A for 8 datasets (7 laboratory, 1 field) reported prior to 1980 was 0.94, for 21 datasets (19 laboratory, 2 field)

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