In the fields of science, engineering, industry and statistics, accuracy is the degree of conformity of a measured or calculated quantity to its actual (true) value. Accuracy is closely related to precision, also called reproducibility or repeatability, the degree to which further measurements or calculations will show the same or similar results. Part of a scientific laboratory at the University of Cologne. ... Engineering is the design, analysis, and/or construction of works for practical purposes. ... Template:Otherusescccc A graph of a bell curve in a normal distribution showing statistics used in educational assessment, comparing various grading methods. ... Conformity is the act of consciously maintaining a certain degree of similarity (in clothing, manners, behaviors, etc. ... In mathematics, a measure is a function that assigns a number, e. ... Quantity is a kind of property which exists as magnitude or multitude. ... Value in mathematics refers to the quantity that is represented by a variable. ... In Wikipedia, precision has the following meanings: In engineering, science, industry and statistics, precision characterises the degree of mutual agreement among a series of individual measurements, values, or results - see accuracy and precision. ... This article is in need of attention from an expert on the subject. ... This page is a candidate to be moved to Wiktionary. ... Various meters Measurement is the estimation or determination of extent, dimension or capacity, usually in relation to some standard or unit of measurement. ... A result is the final consequence of a sequence of actions or events (broadly incidents and accidents) expressed qualitatively or quantitatively, being a loss, injury, disadvantage, advantage, gain, victory or simply a value. ...

The results of calculations or a measurement can be accurate but not precise; precise but not accurate; neither; or both. A result is called valid if it is both accurate and precise. Various meters Measurement is the estimation or determination of extent, dimension or capacity, usually in relation to some standard or unit of measurement. ...

The related terms in surveying are error (random variability in research) and bias (non-random or directed effects caused by a factor or factors unrelated by the independent variable). Statistical surveys are used to collect quantitative information about items in a population. ... Random redirects here. ... In an experimental design, the independent variable (argument of a function, also called a predictor variable) is the variable that is manipulated or selected by the experimenter to determine its relationship to an observed phenomenon (the dependent variable). ...

Accuracy vs precision - the target analogy

High accuracy, but low precision

High precision, but low accuracy

Accuracy is the degree of veracity while precision is the degree of reproducibility. The analogy used here to explain the difference between accuracy and precision is the target comparison. Image File history File links High_accuracy_Low_precision. ... Image File history File links High_accuracy_Low_precision. ... Image File history File links High_precision_Low_accuracy. ... Image File history File links High_precision_Low_accuracy. ... Analogy is either the cognitive process of transferring or giving information from a particular subject (the analogue or source) to another particular subject (the target), or a linguistic expression corresponding to such a process. ...

In this analogy, repeated measurements are compared to arrows that are fired at a target. Accuracy describes the closeness of arrows to the bullseye at the target center. Arrows that strike closer to the bullseye are considered more accurate. The closer a system's measurements to the accepted value, the more accurate the system is considered to be. An arrow is a pointed projectile that is shot with a bow. ... A bullseye on a dartboard. ...

To continue the analogy, if a large number of arrows are fired, precision would be the size of the arrow cluster. (When only one arrow is fired, precision is the size of the cluster one would expect if this were repeated many times under the same conditions.) When all arrows are grouped tightly together, the cluster is considered precise since they all struck close to the same spot, if not necessarily near the bullseye. The measurements are precise, though not necessarily accurate.

However, it is not possible to reliably achieve accuracy in individual measurements without precision — if the arrows are not grouped close to one another, they cannot all be close to the bullseye. (Their average position might be an accurate estimation of the bullseye, but the individual arrows are inaccurate.)

See also Circular error probable for application of precision to the science of ballistics. In the military science of ballistics, Circular Error Probability or circular error probable (CEP) is a simple measure of a weapon systems precision. ... Ballistics (gr. ...

Accuracy and precision in logic level modeling and IC simulation

As described in the SIGDA Newsletter [Vol 20. Number 1, June 1990] a common mistake in evaluation of accurate models is to compare a logic simulation model to a transistor circuit simulation model. This is a comparison of differences in precision, not accuracy. Precision is measured with respect to detail and accuracy is measured with respect to reality. Another reference for this topic is "Logic Level Modelling", by John M. Acken, Encyclopedia of Computer Science and Technology, Vol 36, 1997, page 281-306. hello

Quantifying accuracy and precision

Ideally a measurement device is both accurate and precise, with measurements all close to and tightly clustered around the known value.

The accuracy and precision of a measurement process is usually established by repeatedly measuring some traceable reference standard. Such standards are defined in the International System of Units and maintained by national standards organizations such as the National Institute of Standards and Technology. Traceability refers to the completeness of the information about every step in a process chain. ... Cover of brochure The International System of Units. ... A standards organization, also referred to as standards development organization or SDO, is any entity whose primary activities are developing, coordinating, promulgating, revising, amending, reissuing, interpreting, or otherwise maintaining standards that address the interests of a wide base of users outside the standards development organization. ... NIST logo The National Institute of Standards and Technology (NIST, formerly known as The National Bureau of Standards) is a non-regulatory agency of the United States Department of Commerce’s Technology Administration. ...

Image File history File links No higher resolution available. ...

Precision is usually characterised in terms of the standard deviation of the measurements, sometimes called the measurement process's standard error. The interval defined by the standard deviation is the 68.3% ("one sigma") confidence interval of the measurements. If enough measurements have been made to accurately estimate the standard deviation of the process, and if the measurement process produces normally distributed errors, then it is likely that 68.3% of the time, the true value of the measured property will lie within one standard deviation, 95.4% of the time it will lie within two standard deviations, and 99.7% of the time it will lie within three standard deviations of the measured value. In probability and statistics, the standard deviation of a probability distribution, random variable, or population or multiset of values is a measure of the spread of its values. ... The standard error of a method of measurement or estimate is the estimated standard deviation of the error in that method. ... In statistics, a confidence interval (CI) for a population parameter is an interval between two numbers with an associated probability p which is generated from a random sample of an underlying population, such that if the sampling was repeated numerous times and the confidence interval recalculated from each sample according...

This also applies when measurements are repeated and averaged. In that case, the term standard error is properly applied: the precision of the average is equal to the known standard deviation of the process divided by the square root of the number of measurements averaged. Further, the central limit theorem shows that the probability distribution of the averaged measurements will be closer to a normal distribution than that of individual measurements. A central limit theorem is any of a set of weak-convergence results in probability theory. ... In mathematics and statistics, a probability distribution, more properly called a probability density, assigns to every interval of the real numbers a probability, so that the probability axioms are satisfied. ...

With regard to accuracy we can distinguish:

• the difference between the mean of the measurements and the reference value, the bias. Establishing and correcting for bias is necessary for calibration.
• the combined effect of that and precision

A common convention in science and engineering is to express accuracy and/or precision implicitly by means of significant figures. Here, when not explicitly stated, the margin of error is understood to be one-half the value of the last significant place. For instance, a recording of 843.6 m, or 843.0 m, or 800.0 m would imply a margin of 0.05 m (the last significant place is the tenths place), while a recording of 8436 m, or 8430 m, or 8000 m (or any other integer value) would imply a margin of error of 0.5 m (the last significant place is the ones place). To indicate a less accurate measurement that 0.5 units, one may use scientific notation: '8.0 x 10³ m' indicates a margin of 50 m. In this case, the last significant figure, before multiplying by 10³, is at the first decimal place, but after the multiplication it moves to the hundreds place. Similarly, it is possible to use a multiple of the basic measurement unit: '8.0 km' is equivalent to '8.0 x 10³ m'. In fact, it indicates a margin of 0.05 km (50 m). However, reliance on this convention can lead to false precision errors when accepting data from sources that do not obey it. In statistics, mean has two related meanings: Look up mean in Wiktionary, the free dictionary. ... In statistics, the difference between an estimators expected value and the true value of the parameter being estimated is called the bias. ... Calibration refers to the process of setting the magnitude of the output (or response) of a measuring instrument to the magnitude of the input property or attribute within specified accuracy and precision. ... This article or section is not written in the formal tone expected of an encyclopedia article. ... This article or section does not cite its references or sources. ...

Looking at this in another way, a value of 8 would mean that the measurement has been made with a precision of '1' (the measuring instrument was able to measure only up to 1's place) whereas a value of 8.0 (though mathematically equal to 8) would mean that the value at the first decimal place was measured and was found to be zero. (The measuring instrument was able to measure the first decimal place.) The second value is more precise. Neither of the measured values may be accurate (the actual value could be 9.5 but measured inaccurately as 8 in both instances). Thus, accuracy can be said to be the 'correctness' of a measurement, while precision could be identified as the ability to resolve smaller differences.

Precision is sometimes stratified into:

• Repeatability - the variation arising when all efforts are made to keep conditions constant by using the same instrument and operator, and repeating during a short time period; and
• Reproducibility - the variation arising using the same measurement process among different instruments and operators, and over longer time periods.

As stated before, you can be both accurate and precise. For instance, if all your arrows hit the bull's eye of the target, they are all both near the "true value" (accurate) and near one another (precise). This page is a candidate to be moved to Wiktionary. ... This article is in need of attention from an expert on the subject. ...

Something to think about: In the NFL, a place kicker makes 9 of 10 field goals, and another makes 6 of 10. Even if the 6 that the second kicker made were straight down the middle and the first kicker just made his in, he is still less accurate and less precise than the first kicker. This differs from the darts example because either you make it or you do not; there are not different levels of points that can be scored.

Accuracy in biostatistics

"Accuracy" is also used as a statistical measure of how well a binary classification test correctly identifies or excludes a condition. Binary classification is the task of classifying the members of a given set of objects into two groups on the basis of whether they have some property or not. ...

That is, the accuracy is the proportion of true positives and true negatives in the population. It is a parameter of the test. Scientists recognize two different sorts of error:[1] Statistical error: the difference between a computed, estimated, or measured value and the true, specified, or theoretically correct value (see errors and residuals in statistics) that is caused by random, and inherently unpredictable fluctuations in the measurement apparatus. ... Scientists recognize two different sorts of error:[1] Statistical error: the difference between a computed, estimated, or measured value and the true, specified, or theoretically correct value (see errors and residuals in statistics) that is caused by random, and inherently unpredictable fluctuations in the measurement apparatus. ...

An accuracy of 100% means that the test recognizes all sick and well people as such.