# Deviation

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## deviation

[‚dēv·ē′ā·shən]
(engineering)
The difference between the actual value of a controlled variable and the desired value corresponding to the set point.
(evolution)
Evolutionary differentiation involving interpolation of new stages in the ancestral pattern of morphogenesis.
(optics)
The angle between the incident ray on an object or optical system and the emergent ray, following reflection, refraction, or diffraction. Also known as angle of deviation.
(petroleum engineering)
During a drilling operation, the inclination of the borehole from the vertical.
(statistics)
The difference between any given number in a set and the mean average of those numbers.

## Deviation

in artillery, an accidental phenomenon not allowed for in the laws of dispersion, by which shells (bullets) veer away from the mean trajectory expected under the given firing conditions. Causes of deviation may be the mechanical disruption of the movement of the shell in the bore (for example, separation of the shell from the rifling grooves) or in the air (for example, a defect in the stabilizer fins or other parts), as well as a chance sharp change in weather conditions during the flight of the shell.

## Deviation

in biology, a variety of phylembryogenesis in which a change in the development of an organ arises in the middle stages of its formation and results in a change in the structure of the organ in the adult organism, compared with the same organ in its ancestors. For example, in the middle stages of development the epidermal part of the scale buds of reptiles undergoes keratinization, not ossification (as in sharks). The term “deviation” was introduced by the German scientist F. Müller (1864).

## Deviation

the most common measure of dispersion, that is, deviation from the mean, in mathematical statistics and theory of probability. In the statistical sense, deviation

is the arithmetic mean of the squares of the deviations of the values Xi from their arithmetic mean

In the theory of probability the deviation (variance) of a random variable X is called the expected value E(X - mx)2 of the square of the deviation of X from its expected value mx =E(X). The deviation of a random variable X is denoted by D(X) or by σ2). The square root of the deviation (that is, if the deviation is σ2) is called standard deviation.

For a random variable X with continuous probability distribution, characterized by probability density p(x), deviation is calculated by the formula

where

The following theorem has great significance in the theory of probability: the deviation of the sum of independent terms is equal to the sum of their deviations. No less important is Chebyshev’s inequality, which allows us to evaluate the probability of large deviations of the random variable X from its expected value.

### REFERENCE

Gnedenko, B. V. Kurs teorii veroiatnostei, 5th ed. Moscow, 1969.

## deviation

i. The angular difference between a magnetic and a compass heading. It is a compass error caused by the compass magnet attempting to align with the aircraft's local magnetic field. The deviation error changes with the aircraft heading and the latitude. It is measured in degrees east (+) or west (−), depending on whether the north-seeking end of the compass needle lies to the east or west of magnetic north.
ii. The angle between the wind and the pressure gradient.
iii. In frequency modulation, the amount the carrier increases or decreases when modulated.
vi A departure from a current clearance, such as an off-course maneuver, to avoid bad weather or turbulence.
v A variation from set rules and regulations. Where specifically authorized in the regulation and requested by the pilot, ATC (air traffic control) may permit pilots to deviate from certain regulations.
vi. In flight, a sudden excursion from the normal flight path.
vii. The distance by which a weapon misses its target.
References in periodicals archive ?
In 1981 the Pusat Islam began to identify various sects and groups that were said to be guilty of deviationist teachings (ajaran sesat).
She showed what she called "Cut-ins"-large paper works in which the principal forms, while recognizably Euclidean, showed deviationist tendencies, as if they were political allegories, and bore colors of a kind it might have occurred to an Egyptian dyer to employ so that Joseph's coat should be a chromatic astonishment: porphyry, lapis lazuli, the gold of gold leaf, the orange of sea urchins, malachite green, rose of Sharon, coral pink and the yellow of maize.
Salsberg, in particular, had shown his true colours when he failed to critique the deviationist Gui Caron (a Montreal comrade who had run for the LPP in the Saint Louis riding during the 1948 Quebec provincial election campaign), who had publicly declared that "Marxism failed to explain reality.
This loss of credibility was most aptly illustrated when the state had to re-enact the arms heist of the Al Ma'unah Islamic deviationist group in 2001 to lay to rest widespread rumours that the entire episode had been engineered by the state to stage a crisis.
He did this by destroying the so-called right deviationists led by his former friend Nikolai Bukharin, who had voiced doubts about the frantic pace of collectivization demanded by Stalin.
With support from the capital, centrist deviationists in Georgia were suppressed, along with pretensions toward anything beyond notional autonomy by minority people (especially the Abkhazians).
Xi may well be sincere and the results of the campaign may well be positive, but it is hard from the outside to distinguish it from, say, Mao's self-aggrandizing manoeuvres to label rivals as reactionary deviationists.
Dissidents and deviationists face not an uphill battle but a veritable cliff to break through hardened groupthink just to gain a hearing; often an idea or proposal that is generally dismissed or derided when it comes from a rank-and-file member will be readily and eagerly adopted when that same idea or proposal comes from the Steering Committee or other leading personnel.
Thus pied pipers, some dressed conventionally, others in motley, each calling himself by a different name, have led desperate peasant bands and rebellious journeymen, heretics and deviationists, as often as not mere radical minorities but sometimes whole peoples, to perdition.
Marxist tyrants such as Stalin, Mao, and Pol Pot were aberrations, we are told, deviationists from "true" Marxism.

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