RE: Low Positive Doses in Personnel Monitoring

[paquette@shaman.nexagen.com (Tom Paquette)]

Radsafers,
	Shouldn't badge reporting limits be adjusted for altitude, so 
that the false positive rate is more or less constant across the 
country?
	And that leads to a second question, what is the expected 
control value +/- error for TLD's?
	We had what appeared to have been a "low-valued control" 
subtraction leaving us with a dozen 10 mR readings on body badges, 
which are normally all background.  I sent in 20 control TLD's that had 
been kept in a drawer for the whole quarter and then got my badge 
supplier to give me the instrument readings for these.  They averaged 37 
+/- 7.8 mR SD.  Given this, how does it turn out that 10 mR can have 95% 
probability of being correct?  And how is that single control badges can 
be considered to produce 10 mR readings with 95% probablility of being 
correct?  I have not finished collecting data yet but my working 
hypothesis is that 10 mR is incorrectly applied at this altitude (5300 
ft).  Perhaps my control values are out of line.  Has anyone else 
generated similar data?  I'll be interested to read your comments.


-- 
Tom Paquette, PhD
Senior Scientist, RSO
NeXstar Pharmaceuticals
2860 Wilderness Place
Boulder, C0 80301
paquette@shaman.neXstar.com
biinsite@ix.netcom.com
303-546-7626
Fax 303-444-0672