Kipp&Zonen BSRN Scientific Solar Monitoring System - Manual (Page 171)

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viii. approxim ations and assum ptions incorporated in the m easurem ent m ethod and procedure
ix. variations in repeated observations of the m easurand under apparently identical conditions
Standard Uncertainty
Uncertainty of the result of a m easurem ent expressed as a standard deviation.
Type A evaluation (of uncertainty)
Method of evaluation of uncertainty by the statistical analysis of series of observations.
Type B evaluation (of uncertainty)
Method of evaluation of uncertainty by m eans other than the statistical analysis of series of observations.
Note:
a.
A Type B evaluation of an uncertainty com ponent is usually based on a pool of com paratively reliable
inform ation. For exam ple,
i.
previous m easurem ent data
ii. experience with or general knowledge of the behaviour and properties of relevant m aterials
and instrum ents
iii. m anufacturer’s specifications
iv. data provided in calibration and other certificates
v. uncertainties assigned to reference data taken from handbooks
Combined Standard Uncertainty
Standard uncertainty of the result of a m easurem ent when that result is obtained from the values of
a num ber of other quantities, equal to the positive square root of a sum of term s, ther term s being the
variances or covariances of these other quantities weighted according to how the m easurem ent result
varies with changes in these quantities.
Expanded Uncertainty
Quantity defining an interval about the result of a m easurem ent that m ay be expected to encom pass
a large fractions of the distribution of values that could reasonably be attributed to the m easurand.
Notes:
a.
The fraction m ay be viewed as the coverage probability or level of confidence of the interval.
b. To associate a specific level of confidence with the interval defined by the expanded uncertainty
requires explicit or im plicit assum ptions regarding the probablility distribution characterized by
the m easurem ent result and its com bined standard uncertainty. The level of confidence that m ay
be attributed to this interval can be known only to the extent to which such assum ptions m ay be
justified.
c. Expanded uncertain is term ed overall uncertainty in paragraph 5 of Recom m endation INC-1 (1980).
Coverage Factor
A num erical factor used as a m ultiplier of the com bined standard uncertainty in order to obtain an expanded
uncertainty.
Note:
a. A coverage factor, , is typically in the range 2 to 3.
(Measurable) quantity
Attribute of a phenom enon, body or substance that m ay be distinguished qualitatively and determ ined
quantitatively.
Notes:
a.
The term quantity m ay refer to a quantity in a general sense or to a particular quantity.
b. Quantities that can be placed in order of m agnitude relative to one another are called quantities
of the sam e kind.
c. Quantities of the sam e kind m ay be grouped together into categories of quantities.
Value (of a quantity)
Magnitude of a particular quantity generally expressed as a unit of m easurem ent m ultiplied by a num ber