© 2012AOAC INTERNATIONAL
AOACO
FFICIAL
M
ETHODS
OF
A
NALYSIS
(2012)
G
UIDELINES
FOR
S
TANDARD
M
ETHOD
P
ERFORMANCE
R
EQUIREMENTS
Appendix F, p. 13
ANNEXD
Definitions andCalculations
of HorRat Values from IntralaboratoryData
Excerpted fromDefinitions and Calculations of HorRat Values
from Intralaboratory Data, AOAC INTERNATIONAL, HorRat for
SLV.doc, 2004-01-18.
1. Definitions
1.1 ReplicateData
Data developed under common conditions in the same
laboratory: simultaneous performance, or, if necessary to obtain
sufficient values, same series, same analyst, same day. Such data
provides “repeatability statistical parameters.”
1.2 PooledData
Replicate data developed in the same laboratory under different
conditions but considered sufficiently similar that, for the purpose
of statistical analysis, theymay be considered together. Thesemay
includedifferent runs, different instruments, different analysts, and
different days.
1.3 Average
0 = Sum of the individual values, x
i
, divided by the number of
individual values,
n
.
0= (Σ x
i
)/
n
1.4 StandardDeviation
s
i
= [Σ(x
i
– (
)
2
/
n
]
0.5
1.5 RelativeStandardDeviation
RSD= s
i
100/
1.5.1 RepeatabilityRelativeStandardDeviation [RSD(r) or RSD
r
]
The relative standard deviation calculated from within-
laboratory data.
1.5.2 ReproducibilityRelativeStandardDeviation [RSD(R) or RSD
R
]
The relative standard deviation calculated from among-
laboratory data.
Figure C2. Comparisonof PODmodel terminology toother obsolete terms.
Table D1. Predicted relative standarddeviations
Concentration (C)
Mass fraction (C)
PRSD
R
,%
100%
1.0
2
1%
0.01
4
0.01%
0.0001
8
1 ppm
0.000001
16
10 ppb
0.00000001
32
1 ppb
0.000000001
45
