Biomedical subjects
Publications and source records attributed to W E Potter.
Sometimes the results of measurements in radioactivity are reported as less than MDA. Over the years there have been articles informing the reader that it is incorrect to express the results of measurements as less than MDA. 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 MDA.
Neyman-Pearson principles are briefly discussed and 95% confidence intervals of the form [0, ##.##] are presented. Use is made of the fact that the probability of the difference of two random variables, each with a Poisson distribution, can be expressed in terms of modified Bessel functions of integral order and elementary functions. The validity of the values is discussed.
The work of Fong and Alvarez is easily extended for counting when paired counting is not employed. It remains true in the general case that the precision of a counting method can be no less than about 30% at the LLD and so it is desirable to have decision levels at least several times larger than the LLD so that measurements have sufficient precision to make valid decisions.
Neyman-Pearson principles are briefly discussed and 95% confidence intervals of the form [0, ##.##] are presented. Use is made of the fact that the probability of the difference of two random variables, each with a Poisson distribution, can be expressed in terms of modified Bessel functions of integral order and elementary functions. The validity of the values is discussed.
An improved derivation of the critical levels and detection limits for a two-count method that attempts to measure long-lived activity in the presence of short-lived, naturally occurring progeny of radon is presented. A limitation of the two-count method is also mentioned.