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RE: Acceptance of Data Results
Scott,
Thanks. I have the draft of MARLAP and it only covers the concepts and not the
actual problems associated in application. Chapter 19 is a wonderful
dissertation on statistics in counting and errors associated in sampling and
processing samples. However, in Chapter 18 (18.4.2) the use of Replicates in
Quality Control is addressed. Here the use of the t-test is discussed and the
use of a 2 and 3 sigma control is applied. The problem still exists that when
you have a sample that is 1.8 pCi/g +/- 0.05 and the replicate is 1.4 pCi/g
+/- 0.05, I have failed the analysis precision because according to this test
I have a value of 3.5 which is outside 3sigma. I feel that this is bogus. At
this point I would apply a Relative Percent Difference instead and have a
value of 25% which would be acceptable. My problem is that the USACE wants to
apply the RPD at levels greater than 5x MDC.
This is the type of problem that needs to be addressed. MARLAP and other
directives are great for greater than 3 or 4 pCi, but fail at lower levels.
DAN
<BR>On Mon, 21 Oct 2002 15:37:01 -0500 "Scott, Andrew L CPT AMEDDCS"
<Andrew.Scott@CEN.AMEDD.ARMY.MIL> wrote:<BR><BR>
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<P><FONT SIZE=2>Dan,</FONT>
</P>
<P><FONT SIZE=2>Go to this site, and download Chapter 19 of the MARLAP (draft)
manual. This is on the use of statistics in the lab, and should prove
helpful.</FONT></P>
<P><FONT SIZE=2><A HREF="http://www.eml.doe.gov/marlap/";
TARGET="_blank">http://www.eml.doe.gov/marlap/</A></FONT>
</P>
<P><FONT SIZE=2>Andy</FONT>
</P>
<P><FONT SIZE=2>Andrew L. Scott</FONT>
<BR><FONT SIZE=2>CPT, MS</FONT>
<BR><FONT SIZE=2>Instructor, NBC Sciences</FONT>
</P>
<P><FONT SIZE=2>Academy of Health Sciences</FONT>
<BR><FONT SIZE=2>ATTN: MCCS-HPN</FONT>
<BR><FONT SIZE=2>3151 Scott Rd., Suite 3506B</FONT>
<BR><FONT SIZE=2>Ft. Sam Houston, TX 78234-6142</FONT>
</P>
<P><FONT SIZE=2>210-221-7451/6011</FONT>
<BR><FONT SIZE=2>DSN 471-7451</FONT>
<BR><FONT SIZE=2>FAX x8759</FONT>
<BR><FONT SIZE=2>andrew.scott@cen.amedd.army.mil </FONT>
</P>
<P><FONT SIZE=2>-----Original Message-----</FONT>
<BR><FONT SIZE=2>From: Daniel Mackney [<A
HREF="mailto:photond@EARTHLINK.NET";>mailto:photond@EARTHLINK.NET</A>]</FONT>
<BR><FONT SIZE=2>Sent: Monday, October 21, 2002 14:50</FONT>
<BR><FONT SIZE=2>To: radsafe@list.vanderbilt.edu</FONT>
<BR><FONT SIZE=2>Subject: Acceptance of Data Results</FONT>
</P>
<BR>
<P><FONT SIZE=2>Good day to all!</FONT>
<BR><FONT SIZE=2>Currently, the t-test also called the determination of
Noramlized Absolute</FONT>
<BR><FONT SIZE=2>Difference (NAD) is applied to the sample results at my
radiochemsitry lab. We</FONT>
<BR><FONT SIZE=2>find a problem with samples at or near background (2 to 3
pCi/g). We are</FONT>
<BR><FONT SIZE=2>directed to use the USACE guidance document, but it is
unclear as to this</FONT>
<BR><FONT SIZE=2>problem. </FONT>
<BR><FONT SIZE=2>If anyone knows of a more detailed discussion on the use of
such tests on</FONT>
<BR><FONT SIZE=2>samples and lab replicates, I would be interested. </FONT>
<BR><FONT SIZE=2>Please respond directly to me.</FONT>
<BR><FONT SIZE=2>DAN Mackney</FONT>
<BR><FONT SIZE=2>Radiochemistry Manager</FONT>
<BR><FONT SIZE=2>FUSRAP Maywood Storage Site</FONT>
<BR><FONT SIZE=2>Maywood NJ 07607</FONT>
<BR><FONT SIZE=2>2018434683</FONT>
<BR><FONT SIZE=2>photond@earthlink.net</FONT>
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