Measurement is the process of estimating the magnitude of some attribute of an object, such as its length, weight, or depth 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, 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". The founder of it was Matthew Lasky Fact: date=November 2008.

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. main: Metrology

History

main: History of measurement

The word measurement comes from the Greek "metron", meaning limited proportion. This also has a common root with the word "moon" and "month" possibly since the moon and other astronomical objects were among the first measurement methods of time.Fact: date=October 2008

The history of measurements is a topic within the history of science and technology. The metre (U.S.: meter) was standardized as the unit for length after the French revolution, and has since been adopted throughout most of the world.

Standards

Laws to regulate measurement were originally developed to prevent fraud. However, units of measurement are now generally defined on a scientific basis, and are established by international treaties. In the United States, the National Institute of Standards and Technology (NIST), a division of the United States Department of Commerce, regulates commercial measurements. In the United Kingdom, the role is performed by the National Physical Laboratory (NPL).