120-121 / 164
Table 2
Nominal
T
stat
p
-value
40.5
0.9
40.5
0.9
43.1
-1.7
43.1
-1.7
42.0
-0.6
42.0
-0.6
Mean
41.9
-0.4
SD
1.2
1.2
T
stat
=
where: = mean of the differences between measured results and reference value
sd = standard deviation of the differences between results and reference value
n
= number of replicate analyses of SRM
H
0
: = 0, The null hypothesis is that there is no difference between the measured results and the certified value:
p
-value: is the probability (at the 95% levels of confidence) of obtaining the test statistic assuming that the null hypothesis is true.
p
-value < 0.05 indicate a difference of statistical signifance between measured results and SRM.
95% confidence interval: The true population of the measured value expected to fall within the confidence interval estimate 95% of the time.
lower limit = mean -
upper limit = mean +
where: = critical values of the t-distribution
sd = standard deviation of the differences between results an reference value
n
= number of replicate analyses of SRM
Accuracy - Analytical bias compared to reference material
Certified Reference Material
Measured Results
CRM product
Analyte
Certified value Uncertainty
Concentration
Difference from
certified value
40.6 - 43.1
Bias
Confidence interval
0.4
0.937
0.392
SRM 927e
Tryptophan
41.42
0.848
40.572 - 42.268
Certified range
n
/
sd
d
d
d
n
t
crit
sd
n
t
crit
sd
crit
t
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AMINO-02 (FEBRUARY 2017) - MEF FORM
FOR ERP USE ONLY
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