SPIFAN Nutrients ERP Book 9-29-15

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Table 2
Nominal Tstat p -value
12.3 0.3
12.6 -0.1
13.0 -0.4
12.7 -0.1
12.0 0.5
12.8 -0.2
12.3 0.2
12.2 0.4
12.7 -0.1
Mean 12.5 0.1
SD 0.3 0.3
Tstat =
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
SRM1849a Thiamine 12.57 0.98 11.59 - 13.55
Certified range
12.3 - 12.7
Bias
Confidence interval
-0.1 0.596 0.567
Accuracy - Analytical bias compared to reference material
Certified Reference Material Measured Results
CRM product Analyte Certified value Uncertainty Concentration
Difference from
certified value
n / sd
d
d
d
n
tcrit
sd
n
t crit
sd
crit t
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