"Exact" and approximate methods for analysis of total error in radiation measurements.

Radiation measurement results are typically stated as an estimated activity concentration with an associated 95% error bound. Very frequently, however, the error bound cited at the "95% confidence level" is nothing more than counting error and, especially at higher levels of activity, counting error may constitute a gross understatement of the total error that should reasonably be attributed to the measurement. This paper compares the measurement confidence limits obtained using a typical approximate error propagation procedure with the "exact" confidence limits. A Monte Carlo error propagation method is also considered. The results of the three methods are compared using 222Rn measurement procedures for illustrative purposes.

Detection limit concepts: foundations, myths, and utilization.

Detection limit parameters such as the minimum detectable concentration have been widely discussed in the literature for more than 30 y. Misunderstanding and misapplication of these parameters continue to be widespread and, indeed, even encoded into computer programs, especially those developed in recent years for use with PC-based analyzer boards. This brief review of the principal concepts related to the most common types of detection limits provides guidance for correctly using these parameters. In particular, several myths concerning issues such as the "sample-specific minimum detectable concentration" and the "unreliability" of measurements made below this concentration are discussed.