2008/04/08 by William Edward Potter, William E. Potter, Jadwiga Strzelczyk
Decision Sciences · #Risk and Safety Analysis
paper · doi:10.1097/01.hp.0000304156.82787.96
Sometimes the results of measurements in radioactivity are reported as "less than the minimum detectable activity." Over the years there have been articles informing the reader that it is incorrect to express the results of measurements as less than the minimum detectable activity. A very brief review of past comments on expressing the results of measurements precedes a discussion of why measurements should not be reported as less than the minimum detectable activity. The decision level is the value of the net count above which a measurement process is claimed to have detected activity; it is determined so that the probability of detecting activity, when there is no activity in the sample, is less than or equal to the desired error of the first kind. This article extends previous work restricted to paired counting, where the blank and sample were counted for the same amount of time, to blank count times greater than or equal to the sample count times.