# standard deviation

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Related to Standard deviations: variance, standard error

## deviation

[de″ve-a´shun]
1. a turning away from the regular standard or course.
2. in ophthalmology, strabismus.
3. in statistics, the difference between a sample value and the mean.
axis deviation an axis shift in the frontal plane, as seen on an electrocardiogram. There are three types: Left, from −30° to −90°; Right, from +90° to +180°; and Undetermined, which may be either extreme left or extreme right, from −90° to +180°.
conjugate deviation dysfunction of the ocular muscles causing the two eyes to diverge to the same side when at rest.
sexual deviation sexual behavior or fantasy outside that which is morally, biologically, or legally sanctioned, often specifically one of the paraphilias.
standard deviation (SD) the dispersion of a random variable; a measure of the amount by which each value deviates from the mean. It is equal to the square root of the variance. For data that have a normal distribution, about 68 per cent of the data points fall within (plus or minus) one standard deviation from the mean and about 95 per cent fall within (plus or minus) two standard deviations. Symbol σ.
ulnar deviation a hand deformity, seen in chronic rheumatoid arthritis and lupus erythematosus, in which swelling of the metacarpophalangeal joints causes the fingers to become displaced to the ulnar side. Called also ulnar drift. See illustration. Ulnar deviation (ulnar drift) of the metacarpophalangeal joint, a characteristic sign of rheumatoid arthritis. From Pedretti and Early, 2001.

## stan·dard de·vi·a·tion (SD, σ),

1. statistical index of the degree of deviation from central tendency, namely, of the variability within a distribution; the square root of the average of the squared deviations from the mean.
2. a measure of dispersion or variation used to describe a characteristic of a frequency distribution.

## standard deviation

A statistical term that indicates the relative variability of a value around its mean; the square root of variance.

## standard deviation

Square root of the variance Statistics The most widely used measure of the dispersion of a set of values about a mean, which is equal to the positive square root of the variance, where a graphic representation of the data points is described by a curve with Gaussian distribution–GD–ie, bell-shaped. See Gaussian curve.

## stan·dard de·vi·a·tion

(σ, SD) (stan'dărd dē'vē-ā'shŭn)
1. Statistical index of the degree of deviation from central tendency, namely, of the variability within a distribution; the square root of the average of the squared deviations from the mean.
2. A measure of dispersion or variation used to describe a characteristic of a frequency distribution.

## standard deviation

A measure of dispersion widely used in statistics. Standard deviation is the square root of the arithmetic average of the squares of the deviations of the members of a sample from the mean.

## standard deviation (S)

a measure of the variation in a sample, calculated as the square root of the VARIANCE. Mean values are often followed by the standard deviation.see STANDARD ERROR.

## Standard deviation

A measure of the distribution of scores around the average (mean). In a normal distribution, two standard deviations above and below the mean includes about 95% of all samples.

## stan·dard de·vi·a·tion

(SD) (stan'dărd dē'vē-ā'shŭn)
1. Statistical index of degree of deviation from central tendency, namely, of variability within a distribution; square root of average of squared deviations from mean.
2. Measure of dispersion or variation used to describe a characteristic of a frequency distribution.
References in periodicals archive ?
A valid pooled standard deviation has more degrees of freedom than any of the individual replicate groups from which it is derived, thereby improving the reliability of the estimated standard deviation.
Interestingly enough, both the S-Plus and the alternative standard error estimators appeared to systematically overestimate the standard deviation of [beta].
The precision generated by both standards was well within a single base, with every allele sizing less than 0.13 base standard deviation. However, there were still notable differences in precision with GS-500 when sizing with Local Southern versus Global Southern.
If a stock has a high standard deviation compared to others, it simply means that its actual returns tend to differ largely from its expected return, making it relatively more volatile and riskier.
For in-person classes, instructors' effects on final exam scores vary more than those on course grades, with a standard deviation of 0.49 compared to 0.32.
The extreme spread measured 31 fps and the standard deviation (SD) was 12.8.
A z-score table shows the percentage of the total area under the curve indexed by the number of standard deviations from mean.
They used the Chiras and Manaster (1978) weighted implied standard deviation method to forecast the expected volatility of underlying asset to calculate the theoretical price of an option.
In this issue, Siu and Morash do not use standard deviations at all, but instead use standard errors (sometimes called standard error of the mean).
1/ Historical averages and standard deviations are generally derived over the past 10years, subject to data availability.
Comparative returns and standard deviations (November 2004-October 2012) Year November- May- April October 2005 2.36% 4.34% 2006 8.58% 5.14% 2007 7.58% 4.52% 2008 -10.57% -30.08% 2009 -9.90% 18.72% 2010 14.52% -0.29% 2011 15.24% -8.09% 2012 11.54% 1.02% Sum 39.35% -4.72% Arithmetic average 4.92% -0.59% Annualized return 10.08% -1.18% Annualized std.
She added that some of the kids who participated in the study were two or even three standard deviations away from the average, and their kindergarten indicators were correspondingly worse than those who were one standard deviation away.

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