The Bayesian count rate probability distribution in measurement of ionizing radiation by use of a ratemeter

Recent metrological developments concerning measurement uncertainty, founded on Bayesian statistics, give rise to a revision of several parts of the DIN 25482 and ISO 11929 standard series. These series stipulate detection limits and decision thresholds for ionizing-radiation measurements. Part 3 and, respectively, Part 4 of them deal with measurements by use of linear-scale analogue rate meters. A normal frequency distribution of the momentary rate meter indication for a fixed count rate value is assumed. The actual distribution, which is first calculated numerically by solving an integral equation, differs, however, considerably from the normal distribution although this one represents an approximation of it for sufficiently large values of the count rate to be measured.