Page:NIOSH Manual of Analytical Methods - Chapter P.pdf/15

 The residual corrected

is then given by:

If n is large enough, range

will be small enough that the corrected symmetric accuracy

can be accurately approximated (Eq. 6) as: ,

where the unknown

is: ,

whose confidence limit is now required. First note that the expected value of the first term is:

. Therefore, an estimate

for

can be constructed as:

.

Expressed in terms of

is

Each term can now be identified, forming the basis for an uncertainty budget: the first is the (uncorrected) method uncertainty (squared); the second and third reflect the bias-correction uncertainty owing to finiteness of the validation experiment and the uncertainty in the reference concentration (as here measured n times). A confidence limit

3/15/03

at confidence level

(e.g., 95%) on

222

is now constructed using



NIOSH Manual of Analytical Methods