AOAC SPIFAN Review Team Meeting Book-July 22, 2015

Table 2

Nominal

stat

‐value

2.3

0.0

Mean

2.3

0.0

#DIV/0!

stat

where: = mean of the differences between measured results and reference value

sd = standard deviation of the differences between results and reference value

= number of replicate analyses of SRM

: = 0, The null hypothesis is that there is no difference between the measured results and the certified value:

‐value: is the probability (at the 95% levels of confidence) of obtaining the test statistic assuming that the null hypothesis is true

‐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

= number of replicate analyses of SRM

Difference from

certified value

Confidence interval

‐ #NUM!

0.062

2.231 ‐ 2.355

#DIV/0!

NIST 1849a

Folic Acid

2.293

Bias

Accuracy ‐ Analytical bias compared to reference material

Certified Reference Material

Measured Results

CRM product

Analyte

Certified value

#DIV/0!

#NUM!

0.0

Uncertainty Certified range Concentration

crit

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