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From Wikipedia, the free encyclopedia
(Redirected from Measurements)
Measurement is the process of estimating the magnitude of some attribute of an object, such as its length or weight, relative to some standard (unit of measurement), such as a meter or a kilogram. The term is also used to indicate the number that results from that process. Metrology is the scientific study of measurement. The act of measuring usually involves using a measuring instrument, such as a ruler, weighing scale, thermometer, speedometer, or voltmeter, which is calibrated to compare the measured attribute to a measurement unit. Any kind of attributes can be measured,[1] including physical quantities such as distance, velocity, energy, temperature, or time. The assessment of attitudes or perception in surveys, or the testing of aptitudes of individuals are also considered to be measurements. Indeed, surveys and tests are considered to be "measurement instruments".
Measurements always have errors and therefore uncertainties. In fact, the reduction not necessarily the elimination of uncertainty is central to the concept of measurement. Measurement errors are often assumed to be normally distributed about the true value of the measured quantity. Under this assumption, every measurement has three components: the estimate, the margin of error or uncertainty or error bound, and the confidence level that is the probability that the actual magnitude lies within the margin of error. For example, a measurement of the length of a plank might result in an estimate of 2.53 meters plus or minus 0.01 meter, with a level of confidence of 99%.
The initial state of uncertainty, prior to any observations, is necessary to assess when using statistical methods that rely on prior knowledge (Bayesian methods). This can be done with calibrated probability assessment.
Measurement is fundamental in science; it is one of the things that distinguish science from pseudoscience. It is easy to come up with a theory about nature, hard to come up with a scientific theory that predicts measurements with great accuracy. Measurement is also essential in industry, commerce, engineering, construction, manufacturing, pharmaceutical production, and electronics.
When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the state of science.
Lord Kelvin
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