Question

What is the formula for relative expanded uncertainty?

(a) Ur = U/| y |

(b) Ur = U/y

(c) Ur = U*| y |

(d) Ur = U*2y

This question was posed to me during an interview.

This is a very interesting question from Expanded Uncertainty in portion Evaluating Uncertainty in Measurement of Engineering Metrology

Answer 1

Right choice is (a) Ur = U/| y |

To explain I would say: In analogy with relative standard uncertainty Ur  and relative combined standard uncertainty Uc,r the relative expanded uncertainty of a measurement result y is Ur = U/ | y |, y is not equal to zero  and U is expanded uncertainty.