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Re: Turner's Book and Counting Statistics
I agree that Turner's 2nd edition contains the best introduction to statistics
I've ever seen. In particular, the insights or statistical fluctuations in
radioactivity counting problems given in the first eight sections of Chapter 11
and in Appendix E are the clearest exposition I have ever seen in one place. I
use the text in "Introduction to Radiological Science," and advanced
undergraduate - beginning grad course that I teach at Washington State
University - Tri-Cities.
However, Turner's "exact" formulations of the minimum detectable amount (MDA -
Turner calls this "minimum detectable true activity") given in Equation 11.78
and decision level (DL - Turner calls this "minimum significant measured
activity") given in Equation 11.68 are not correct, due to incorrect assumptions
in equations 11.65 and 11.67. The first term in the radical should not be rg/tg
when determining the decision level, but rb/tg. My finding has been confirmed
by Paul Stansbury, Allen Brodsky and Ken Skrable, and can be seen in standard
references such as ANSI N13.30, Performance Standard for Radiobioassay. It is
easy to convince oneself that this is the case by doing "what if" calculations
letting tg = tb, tg = 1000*tb and tg = tb/1000: the answers are not plausible.
That being said, I still highly recommend Turner's book.
Those desiring a [revised] copy of the handout "False Alarms, True Alarms, and
Statistics: Correct Usage of Decision Level and Minimum Detectable Amount," a
continuing education lecture I gave at the Health Physics Society meeting in
Minneapolis on July 15, 1998 can download it from
http://www.pnl.gov/bayesian/Strom/Stat-CEL-DJStrom.PDF.
- Dan Strom
The opinions expressed above, if any, are mine alone and have not been reviewed
or approved by Battelle, the Pacific Northwest National Laboratory, or the U.S.
Department of Energy.
Daniel J. Strom, Ph.D., CHP
Adjunct Associate Professor, Environmental Sciences and Regional Planning
Washington State University - Tri-Cities
and
Risk Analysis & Health Protection Group, Environmental Technology Division,
Pacific Northwest National Laboratory
Mail Stop K3-56, PO BOX 999, Richland, Washington 99352-0999 USA
Telephone (509) 375-2626 FAX (509) 375-2019 daniel.j.strom@pnl.gov
http://www.pnl.gov/bayesian http://qecc.pnl.gov http://bidug.pnl.gov
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