5. A follow-up study was conducted of 3,000 military troops deployed at an atomic test site in Nevada to detect the occurrence of leukemia. A total of 1,870 persons were successfully traced by the investigators, and an additional 443 contacted the investigators on their own as a result of publicity about the study. Four cases of leukemia occurred among the 1,870 individuals traced by the investigators, and an additional four occurred among those individuals who contacted the investigators on their own. Could interpretation of the study results be subject to bias