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Re: DOE Sites Reporting a less than number
I have a very informative publication titled " Upgrading Environmental
Radiation," Health Physics Society Committee Report HPSR-1, 1980 (EPA
520/1-80-012). The report "Reporting of Environmental Radiation
Measurements Data" is the most useful I have ever ran across (pages 6-1 to
6-33). Here is a snippet with regards to LLD/MDC:
Page 6-27 to 6-28, Misapplication of the LLD or MDC for A Posteriori
Decisions:
p. 6-27
"As stated earlier, the LLD is an a priori estimate dependent on only the
instrument background and detection efficiency, and the MDC is an a priori
estimate for a given type of analysis or measurement process under
specified typical conditions. They are not a posteriori decision limits for
every measurement. They need not, and should not, therefore, be calculated
for each individual measurement. The practice of comparing a unique
computed LLD or MDC for each measurement against the measurement result
should be avoided."
p. 6-28
"...it is recommended that for every measurement result should be recorded
and reported directly as found.. "Less than the LLD," "not detected" and
similar expressions should not be used in reporting data. This does not
imply that the activity in the sample is truly less than some absolute
level that can be detected. Rather, it merely indicates that this
particular measurement resulted in a single value which was less than an
estimated LLD or MDC for the measurement procedure."
Purist or practical? Comments? Has this view been changed with regards to
the statistical treatment of data (the publication is dated 1980)? Perhaps
"wisdom is learning what to overlook" (William James)...
DJWhitfill
Opinions expressed are mine and do not reflect official policies or
positions of the Kansas Department of Health and Environment.
William V Lipton
<liptonw@dteenergy To: Multiple recipients of list
.com> <radsafe@romulus.ehs.uiuc.edu>
Sent by: cc:
radsafe@romulus.eh Subject: Re: DOE Sites Reporting a less than
s.uiuc.edu number
08/28/00 11:13 AM
Please respond to
radsafe
When a survey value is quoted as "less than x," this implies that no
activity was detected with a MDA of x. To me, this is the best way to
report negative results.
The opinions expressed are strictly mine.
It's not about dose, it's about trust.
Bill Lipton
liptonw@dteenergy.com
Dave Biela wrote:
> We recently got hit during a DOE audit for reporting a "less than" number
on a survey form. For example we have a smear-able release limit of 200
dpm/100cm-sq beta, if we see nothing, we use less than. How do you do it
at other sites? Have you run into the same audit comments? Any regulatory
paragraph references would be appreciated.
>
> RADSAFE please respond directly to me at:
>
> bielad@wv.doe.gov
>
> Thanks
> Dave Biela
>
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information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html