[ RadSafe ] Validity / Usefulness of a result....

Pete_Bailey at fpl.com Pete_Bailey at fpl.com
Tue May 1 08:29:40 CDT 2007

Consider a 'periodic sampling of a tank' situation.
Often, the results are quite low, not much over MDA.

Attempting to set up an extremely simple
guideline for 'the least experienced / least trained'
lab person to deal with....

The process I'm attempting to adress:
      ( sample resuts are R +- r ,  r is 2 sigma)
   two results,  R1 =-r1   and  R2 +- r2

Determine if the difference between R1 and R2 is 'real' . . .

The 'statistics book' stuff is easy
     (can get tangled in square root of sum of squares...)

But I'm Thinking of testing any one result for 'confidence'
before doing the math.

I'm thinking of situations where subsequent
results are 'kinda close'....

    IF  R2/r2 exceeds 50%, the result shouldn't be used;
       wait untill next sample and compare R1 and R3

   IF  R2/r2 = or exceeds 25% (but < 50%), can compare
      R1 and R2, but should wait until R3 is available
      to draw firm (actionable) conclusions .

    IF R/r is less than 25 %, then go for it....

OR should I let them use the result, no matter how big  r  is,
and let the test of differences 'sort it out'  ?

Also, I'm looking for support of the 'break points' (25% , 50%) I 'choose'.



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