SPIFAN Nutrients ERP Book_9-29-15

BVit-02 - MEF FORM FOR ERP USE ONLY DO NOT DISTRIBUTE

Table 2

Accuracy - Analytical bias compared to reference material Certified Reference Material

Measured Results

T stat Bias

Difference from certified value

CRM product

Analyte

Certified value Uncertainty Certified range Concentration

Confidence interval

p -value

Nominal

990 987

90.1 92.8 38.8 76.0

1041 1004 1074 1067 1079 1117

6.3

13.3

SRM 1849a

Niacin (ug/100g)

1080

100

980 - 1180

-50.3

3.792

0.003

1000.5 - 1058.9

1.4

-37.3 100.9 103.1

979 977

1030 1012

49.8 68.5

Mean

1029.7

50.3

SD

46.0

46.0

d

=

T stat

/ sd

n

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 d

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

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.

sd

sd

t crit

t crit

lower limit = mean -

upper limit = mean +

n

n

t

where: = critical values of the t-distribution

crit

sd = standard deviation of the differences between results an reference value n = number of replicate analyses of SRM

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