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Table 2
Nominal
T
stat
p
‐value
104.5
3.6
Mean
104.5
3.6
SD
#DIV/0!
#DIV/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
Difference from
certified value
Confidence interval
‐ #NUM!
9.92
98.21 ‐ 118.05
#DIV/0!
NIST SRM 1849a
Niacin
108.13
Bias
Accuracy ‐ Analytical bias compared to reference material
Certified Reference Material
Measured Results
CRM product
Analyte
Certified value
#DIV/0!
#NUM!
‐3.6
Uncertainty Certified range Concentration
n
/
sd
d
d
d
n
t
crit
sd
n
t
crit
sd
crit
t
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