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8 Recommendations A. REPORTING OF BIAS AND UNCERTAINTY For each test series, this report lists the best estimate of the overall bias, B. for correcting film badge readings and converting them to deep-dose equivalents. It also lists the best estimate of the uncertainty, K, which quantifies the range of uncertainty at the 95% confidence level for these bias-adjusted values. Values assigned to both B and K take into account the specific exposure conditions and sources of uncertainty for each series. To obtain the best estimate of the deem dose equivalent in rem, the reported film badge exposure in R is divided by the overall bias, B. To obtain the upper and lower limits of uncertainty at the 95% confidence level, this calculated best estimate of the deep-dose equivalent is multiplied by K and divided by K, respectively. The Committee recommends that these calculations be performed for each reported exposure under investigation. Tables for converting reported individual film badge exposures are provided for each test series in Chapter 6. B. TREATMENT OF EXPOSURES REPORTED AS BELOW MINIlVIUlV! DETECTABLE LEVELS OR AS ZERO The general recommendation of the Committee in circumstances where a large number of readings below the minimum detectable level (MDL) appear in a participant's record, or where the MDL is unusually high, due to unusual environ- mental circumstances, is to allot one-half of the MDL for each zero appearing in 191
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192 FILM BADGE DOSIMETRY mr ATMOSPHERIC NUCLEAR TESTS the record (Section 5.C). For consistency, recorded film badge readings below the MDL also should be interpreted as one-half the MDL, since, in fact, these readings are not distinguishable from zero. A review of the e~osure-reading distribution for all test series leads the Committee to conclude that such a practice would probably overestimate the actual exposure, but that it would not greatly exaggerate the general results in any test series or the recorded exposure of any single participant. In special circumstances such as when the overwhelming majority of readings for a group of participants similarly exposed during a given exposure period were zero, zero is probably the reading of choice in terms of maximum accuracy and should be used accordingly. The Committee emphasizes that this treatment of reported exposures below the MDL for assessment purposes is suggested only in individual cases where there is reason to investigate possible biological effects attributable to the radiation dose. It does not recommend changes to existing records. C. UNCERTAINTIES IN THE SUMMATION OF SEVERAL FILM BADGE READINGS Determination of an individual's total deep-dose equivalent will often require the summation of deep-dose equivalents obtained from more than one film badge reading. For this total, the upper and lower confidence limits can be estimated by summing the upper and lower 95% confidence limits for the individual assess- ments of deep-dose equivalent. It should be noted that this procedure will over- esiimate the range of uncertainty at the 95% confidence level.