# Dictionary Definition

accuracy

### Noun

1 the quality of nearness to the truth or the
true value; "he was beginning to doubt the accuracy of his
compass"; "the lawyer questioned the truth of my account" [syn:
truth] [ant: inaccuracy]

2 (mathematics) the number of significant figures
given in a number; "the atomic clock enabled scientists to measure
time with much greater accuracy"

# User Contributed Dictionary

## English

### Pronunciation

### Noun

- The state of being accurate; freedom from mistakes, this exemption arising from
carefulness; exact
conformity to truth, or to a rule or model; precision; exactness; nicety; correctness
- The value of testimony depends on its accuracy.

#### Translations

state of being accurate

- Czech: přesnost
- Finnish: tarkkuus
- French: exactitude
- German: Genauigkeit
- Hungarian: pontosság, helyesség, precizitás
- Indonesian: ketelitian, ketepatan, kecermatan, keakuratan
- Interlingua: exactitude, precision
- Italian: esattezza
- Japanese: 正確性 (せいかくせい, seikaku-sei), 正確さ (せいかくさ, seikaku-sa), 精密性 (せいみつせい, seimitsu-sei), 精密さ (せいみつさ, seimitsu-sa), 確度 (kakudo)
- Maltese: eżattezza
- Norwegian: nøyaktighet
- Polish: dokładność
- Portuguese: exatidão, precisão, correção
- Romanian: precizie , acuratete
- Spanish: exactitud
- Swedish: noggrannhet
- Telugu: ఖచ్చితత్వం (khachchitatvam)

# Extensive Definition

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
show the same or similar results. 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. 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).

## Accuracy vs precision - the target analogy

In many cases precision can be characterised in
terms of the standard
deviation of the measurements, sometimes incorrectly called the
measurement process's
standard error. The smaller the standard deviation, the higher
the precision. In some literature, precision is defined as the
reciprocal
of variance, while many
others still confuse precision with the confidence
interval. 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.

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.

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 would imply a margin of
error of 0.5 m (the last significant digits are the units).

A reading of 8000 m, with trailing zeroes and no
decimal point, is ambiguous; the trailing zeroes may or may not be
intended as significant figures. To avoid this ambiguity, the
number could be represented in scientific notation: '8.0 x 10³ m'
indicates that the first zero is significant (hence a margin of 50
m) while '8.000 x 10³ m' indicates that all three zeroes are
significant, giving a margin of 0.5 m. 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.

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.

A common way to statistically measure precision
is a Six
Sigma tool called ANOVA
Gage R&R. 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).

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 binary classification

"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 true
results (both true
positives and true
negatives) in the population. It is a parameter of the
test.

- =\frac

An accuracy of 100% means that the test
identifies all sick and well people correctly.

Also see Specificity
(tests) and Sensitivity
(tests).

Accuracy may be determined from Sensitivity and
Specificity, provided Prevalence is known, using the
equation:

- =()() + ()(1-)

The accuracy
paradox for predictive
analytics states that predictive models with a given level of
accuracy may have
greater predictive
power than models with higher accuracy. It may be better to
avoid the accuracy metric in favor of other metrics such as
precision and recall.

## Accuracy and precision in psychometrics

In psychometrics the terms accuracy and precision are interchangeably used with validity and reliability respectively. Validity of a measurement instrument or psychological test is established through experiment or correlation with behavior. Reliability is established with a variety of statistical technique (classically Cronbach's alpha).## See also

- Calculation of glass properties - Decreasing accuracy of experimental data in modern scientific publications for some glass properties

## References

accuracy in German: Präzision

accuracy in German: Genauigkeit

accuracy in Spanish: Precisión y exactitud

accuracy in French: Calcul d'incertitude

accuracy in Dutch: Nauwkeurigheid en
precisie

accuracy in Japanese: 正確度と精度

accuracy in Portuguese: Exactidão

accuracy in Russian: Точность

accuracy in Slovenian: točnost in
natančnost

accuracy in Finnish: Tarkkuus

# Synonyms, Antonyms and Related Words

absoluteness, attention to
detail, attention to fact, care for truth, circumstantiality,
conscientiousness,
correctness,
criticality,
criticalness,
definiteness,
delicacy, detail, exactingness, exactitude, exactness, exquisiteness, faithfulness, faultlessness, fidelity, fineness, finicality, finicalness, finickiness, finickingness, flawlessness, fussiness, literalism, literality, literalness, mathematical
precision, meticulousness, minuteness, minuteness of
detail, niceness,
nicety, particularity, particularness, perfection, preciseness, precisianism, precision, punctiliousness,
punctuality,
refinement, right, rightness, rigidity, rigidness, rigor, rigorousness, scrupulosity, scrupulousness, severity, specificity, strictness, subtlety, textualism, the
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