Analysis of ANSI N13.11: the performance algorithm

The method of performance testing for personnel dosimeters specified in draft ANSI N13.11, Criteria for Testing Personnel Dosimetry Performance is evaluated. Points addressed are: (1) operational behavior of the performance algorithm; (2) dependence on the number of test dosimeters; (3) basis for choosing an algorithm; and (4) other possible algorithms. The performance algorithm evaluated for each test category is formed by adding the calibration bias and its standard deviation. This algorithm is not optimal due to a high dependence on the standard deviation. The dependence of the calibration bias on the standard deviation is significant because of the low number of dosimeters (15) evaluated per category. For categories with large standard deviations the uncertainty in determining the performance criterion is large. To have a reasonable chance of passing all categories in one test, we required a 95% probability of passing each category. Then, the maximum permissible standard deviation is 30% even with a zero bias. For test categories with standard deviations <10%, the bias can be as high as 35%. For intermediate standard deviations, the chance of passing a category is improved by using a 5 to 10% negative bias. Most multipurpose personnel dosimetry systems will probably require detailed calibration adjustments to pass all categories within two rounds of testing