Nevertheless, we have taken additional steps to assure the quality of the participant identification process. This process included a comparison between the current (1994) data set and the 1986 data set, as well as comparisons with two other sources of participation information—a roster of CROSSROADS participants from the National Association of Atomic Veterans (NAAV) and a roster compiled from direct solicitation of information from veterans by MFUA.

Methodology

Comparison to Previous Versions of the Participant Roster

By comparing the current participant data set to the 1986 version and seeking verification of participation for sampled individuals, we were able to estimate a crude false positive rate and better understand changes that have occurred in the participant cohort over time. We drew a sample of 50 participants from each of the following categories:

  • Participants who were found in both the 1986 participant list and in the current, 1994, participant list (matched, n = 39,844). Matched participants were defined by a corresponding first and last name and other confirmatory information such as military service number, date of birth, and unit of assignment. Allowances were made for obvious typographical errors (for example, "Johsnson, John" was accepted as a match to "Johnson, John" if there was also a match on service number or other confirming evidence).
  • Participants who are currently in the study but could not be matched to a 1986 participant (n = 2,713; new-only's).
  • Participants who were in the study in 1986 but could not be matched to a participant in the 1994 file (n = 667; old-only's).

MFUA requested documentation from NTPR to verify the status of each of the selected individuals. We then categorized every putative participant as a verified participant, a verified nonparticipant, or a person whose participation could not be verified using written documentary sources. To get a false positive rate we then calculated the fraction of inappropriately classified participants in the matched and new-only samples.

Comparison of Participant Roster to National Association of Atomic Veterans (NAAV) Mortality Study List

Estimating the number of persons erroneously left out of the study was more difficult than verifying the participation of those whose names were already known to be on the participant list. To estimate the false negative rate—



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