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From Latin praecisĭo, the precision is the necessity and obligation of accuracy and conciseness when executing something . For the engineering and the statistics However, precision and accuracy are not synonyms.

The precision in this sense, is the dispersion of the set of values ​​that is obtained from repeated measurements of a magnitude: The lower the dispersion, the more precise . Accuracy, on the other hand, refers to the proximity of the measured value to the real value.

For the computing , precision is the amount of bits used to represent a value. The philosophy Instead, he argues that precision is a mental abstraction that makes the understanding of two things identified, one distinct from the other.

In everyday language, precision is conciseness and accuracy in some aspect or thing. For example: “The forward fired with amazing precision and scored from a distance greater than twenty meters ”, "Larry Bird was an NBA player with great precision in his three-point shot", "Please try to speak accurately so we can understand what happened last night", “Precision is not one of its virtues: he wanted to explain how to get to the restaurant and we ended up lost”.

In the field of sciences in general, accuracy is the ability of an instrument to obtain the same result in different measurements , developed under the same conditions. It is known as precision machine to a device built with the aim of obtaining exact results. The difference between the measured value and the actual value is called the measurement error.

Measurement errors

The mistakes of measurement they may appear during the use of measuring instruments, devices created to perform the comparison of physical quantities, and the causes for which they occur are diverse. It is possible to distinguish between two major types of measurement errors: systematic, associated with the accuracy of the measurement. They are predictable and can be calculated and eliminated through calibration and compensation processes; the random, linked to the precision of the instruments. It is not possible to foresee them, since their causes are unknown.

Continuing with random errors, also called stochasticThere may be two situations: that their level of complexity is considerable, which makes it difficult to find the right techniques to understand their causes; that its impact on the final result is small, and that it does not justify the investment of weather to find a solution

The first step to approach an error of this type is to carry out a sampling of measurements, a technique that aims to select a sample from a population, name that receives the set of the elements that are taken as the basis for the observations. Using the data collected in the measurements it is possible to calculate the average and the standard deviation, two parameters that allow to find the Gaussian distribution, a resource used to thoroughly analyze phenomenon Natural, social and psychological.

While it is not always possible to find all Causes of a measurement error, there are four fundamental points that encompass the most common origins of failures and allow focusing research on a more defined line; Errors may be due to:

* problems with him instrument of measurement used, among which are design and manufacturing errors, alignment, or those caused by the conditions of the instrument itself;

* the operator. In this case, it may well be an incorrect positioning or a problem during reading;

* certain environmental factors, such as an alteration of the temperature (which can cause dilation and contraction of materials such as metal), atmospheric pressure or humidity;

* the geometric tolerance values ​​of a given piece (the range in which there is no rejection towards other components), among which is the deformation due to the application of inadequate forces.

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