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Examples of uncertainty statements
The following are examples of uncertainty statements as would
be used in publication or correspondence. In each case, the quantity
whose value is being reported is assumed to be a nominal 100 g
standard of mass ms.
Example 1
ms = 100.021 47 g with a combined standard uncertainty (i.e., estimated
standard deviation) of uc = 0.35 mg. Since it can be assumed that the possible estimated
values of the standard are approximately normally distributed
with approximate standard deviation uc, the unknown value of the standard is believed to lie in the interval
ms ± uc with a level of confidence of approximately 68 %.
Example 2
ms = (100.021 47 ± 0.000 70) g, where the number following the symbol
± is the numerical value of an expanded uncertainty U = k uc, with U determined from a combined standard uncertainty (i.e., estimated
standard deviation) uc = 0.35 mg and a coverage factor k = 2. Since it can be assumed that the possible estimated values
of the standard are approximately normally distributed with approximate
standard deviation uc, the unknown value of the standard is believed to lie in the interval
defined by U with a level of confidence of approximately 95 %.
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