Mẫu chuẩn thành phần kim loại SRM 1258-I
Certified Mass Fraction Values: Certified values for constituents in SRM 1258-I are provided in Table 1 as mass
fractions of the total amounts of the elements in an aluminum matrix [1]. A NIST certified value is a value for which
NIST has the highest confidence in its accuracy, in that all known or suspected sources of bias have been taken into
account [2]. A certified value is the present best estimate of the true value. The certified values are metrologically
traceable to the derived SI unit of mass fraction, expressed in %. The uncertainty listed with each value is an expanded
uncertainty calculated by combining a between-method variance [3] with a pooled, within-method variance following
the ISO/JCGM Guide [4]. The expanded uncertainty is expressed at the 95 % confidence level, using the coverage
factor, k.
Table 1. Certified Values for SRM 1258-I
Elements Mass Fraction
(%)
Expanded Uncertainty
(%)
Coverage Factor
k
Silicon (Si) 0.80 0.04 2.4
Iron (Fe) 0.080 0.003 2.6
Copper (Cu) 0.848 0.010 2.4
Manganese (Mn) 0.481 0.010 2.1
Magnesium (Mg) 1.00 0.03 2.3
Zinc (Zn) 1.03 0.02 2.4