Re: It seems that my previous message was incomplete - here is the

["Sandy Perle" <sandyfl@earthlink.net>]

Hello Du Toit. Sorry you weren't able to be at the meeting in 
Hershey, PA this year.

> Therefore the possibility that you would report the length of the object
> incorrectly, and that the difference between your reported value and the
> actual value is greater than some limit (false positive) or smaller
> (false negative), would be greater (worse accuracy and precision) for
> the ruler with the 5 mm divisions.

The only argument I will put forth regarding the above (which by 
itself is correct) has to do with the added factor with a dosimetry 
measurement that results in a measurement by 2 or more of the same 
type of dosimeters (the actual personnel dosimeter as well as 1 or 
more Control badges). Each dosimeter has its own unique set of 
variables that all contribute to a measurement of uncertainty, and 
when combined, based on the lower limit established, are more likely 
to result not only in a false positive, but also in a false negative 
as well. The degree of these are based on how close to the zero point 
the dosimeter can measure, and how close to the actual calculated LLD 
one can measure and then use for reporting purposes.

The answer really can't be quantified, since there are numerous 
variables that must be considered, including the dosimeter 
manufacturer, age, lighting conditions, exposure exposed to, the 
Controls, the facility background variation, the reader itself, the 
irradiator used to irradiate the QA dosimeters, fading issues, etc. 
These all must be considered and are far more important than the LLD, 
which in the end, the calculated value is far less than what would be 
in practice, used as the MRD.

------------------------------------------------------------------------
Sandy Perle					Tel:(714) 545-0100 / (800) 548-5100   				    	
Director, Technical				Extension 2306 				     	
ICN Worldwide Dosimetry Division		Fax:(714) 668-3149 	                   		    
ICN Biomedicals, Inc.				E-Mail: sandyfl@earthlink.net 				                           
ICN Plaza, 3300 Hyland Avenue  		E-Mail: sperle@icnpharm.com          	          
Costa Mesa, CA 92626                                      

Personal Website:  http://www.geocities.com/capecanaveral/1205
ICN Worldwide Dosimetry Website: http://www.dosimetry.com

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