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Fonterra Co-operative Group
Page 8
Figure 5: Linearity and residuals plots for vitamin D
3
linearity experiment 2
Figure 6: Linearity and residuals plots for vitamin D
3
linearity experiment 3
Precision
Repeatability refers to the degree of agreement of results when conditions are maintained as constant as
possible. Precision was only evaluated for vitamin D
3
since none of the SPIFAN kit samples were fortified
with vitamin D
2
.
The repeatability standard deviation (S
r
) was calculated as in equation 1:
S
r
=
n
d
n
i
2
1
2
¦
equation 1
where:
d
i
= is the difference between duplicate results for the sample i
n = number of pairs of duplicates
The repeatability relative standard deviation (RSD
r
) for the method is calculated below in equation 2:
y = 1.537x - 0.1227
R² = 0.9989
0
5
10
15
20
25
30
35
40
45
50
0.0
10.0
20.0
30.0
Peak Area Ratio
Concentration Ratio
Linearity: Vitamin D
3
29
th
Dec 2015
-1.2
-0.6
1E-15
0.6
1.2
0.0
20.0
40.0
60.0
Residuals
XVariable
Residual Plot: Vitamin D
3
29
th
Dec
2015
y = 1.4096x - 0.1562
R² = 0.9999
0
5
10
15
20
25
30
35
40
45
0.0
10.0
20.0
30.0
Peak Area Ratio
Concentration Ratio
Linearity: Vitamin D
3
5
th
Jan 2016
-0.2
-0.1
0
0.1
0.2
0.0
20.0
40.0
60.0
Residuals
XVariable
Residual Plot: Vitamin D
3
5
th
Jan 2016
VitD-18 (February 2016)
FOR ERP USE ONLY
DO NOT DISTRIBUTE