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5
EXAMPLE
Consider the March subset of ‘AOAC-C01-Fat-Data.csv’. There are two replicates for each
collaborator, and the average of these is the results analyzed for reproducibility effects.
Repeatability is measured by the difference in replicate pairs. It will be assumed for purposes of
illustration that all collaborators all used the same test method for fat.
There are 42 collaborators, with average results ranging from 13.08 to 36.08 percent fat, with
median and mean results 14.42 and 15.10.
Using method 2), the repeatability standard deviation s
r
is 0.4739, the apparent intercollaborator
standard deviation s is 3.503, and the repeatability adjusted value for reproducibility standard
deviation is 3.519.
The boxplot and normal Q-Q plot for these data are:
15
20
25
30
35
March
-2 -1 0 1 2
15
20
25
30
35
March
Theoretical Quantiles
SampleQuantiles
107