362-363 / 620
Table 2
Nominal
T
stat
p
-value
105.0
4.0
104.0
5.0
105.0
4.0
108.0
1.0
106.0
3.0
102.0
7.0
108.0
1.0
103.0
6.0
106.0
3.0
Mean
105.2
3.8
SD
2.0
2.0
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
SRM 1849a (Only first 9 replicates fit into spreadsheet) Total Choline
109
Bias
Accuracy - Analytical bias compared to reference material
Certified Reference Material
Measured Results
CRM product
Analyte
Certified value Uncertainty Certified range Concentration
Difference from
certified value
Confidence interval
- 106.8
11
98 - 120
5.534
0.001
103.6
-3.8
n
/
sd
d
d
d
n
t
crit
sd
n
t
crit
sd
crit
t
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