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Accuracy is also used as a statistical measure of how well a binary classification test correctly identifies or excludes a condition. That is, the accuracy is the proportion of correct predictions (both true positives and true negatives) among the total number of cases examined. [10] As such, it compares estimates of pre- and post-test probability.
The formal definition of calibration by the International Bureau of Weights and Measures (BIPM) is the following: "Operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties (of the calibrated instrument or ...
The measurement of length or size, force, mass, electrical and other properties is included in Nanometrology. The problem is how to measure these with reliability and accuracy. The measurement techniques used for macro systems cannot be directly used for measurement of parameters in nanosystems.
In a classification task, the precision for a class is the number of true positives (i.e. the number of items correctly labelled as belonging to the positive class) divided by the total number of elements labelled as belonging to the positive class (i.e. the sum of true positives and false positives, which are items incorrectly labelled as belonging to the class).
For instance, the accuracy of land-survey distance measurements when using a laser rangefinder might be 1 millimeter per kilometer of distance; this could be expressed as "Accuracy = 1 ppm." [a] Parts-per notations are all dimensionless quantities: in mathematical expressions, the units of measurement always cancel.
It is also possible to measure frequency using the same techniques in software in an embedded system. A central processing unit (CPU), for example, can be arranged to measure its own frequency of operation, provided it has some reference timebase to compare with. Accuracy is often limited by the available resolution of the measurement. The ...
Accuracy can be seen as just one element of IQ but, depending upon how it is defined, can also be seen as encompassing many other dimensions of quality. If not, it is perceived that often there is a trade-off between accuracy and other dimensions, aspects or elements of the information determining its suitability for any given tasks.
The accuracy of micrometers is checked by using them to measure gauge blocks, [17] rods, or similar standards whose lengths are precisely and accurately known. If the gauge block is known to be 0.75000 ± 0.00005 inch ("seven-fifty plus or minus fifty millionths", that is, "seven hundred fifty thou plus or minus half a tenth"), then the ...