# standard deviation

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## standard deviation

[′stan·dərd ‚dē·vē′ā·shən]
(statistics)
The positive square root of the expected value of the square of the difference between a random variable and its mean.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

## standard deviation

see MEASURES OF DISPERSION.
Collins Dictionary of Sociology, 3rd ed. © HarperCollins Publishers 2000

## standard deviation

(statistics)
(SD) A measure of the range of values in a set of numbers. Standard deviation is a statistic used as a measure of the dispersion or variation in a distribution, equal to the square root of the arithmetic mean of the squares of the deviations from the arithmetic mean.

The standard deviation of a random variable or list of numbers (the lowercase greek sigma) is the square of the variance. The standard deviation of the list x1, x2, x3...xn is given by the formula:

sigma = sqrt(((x1-(avg(x)))^2 + (x1-(avg(x)))^2 + ... + (xn(avg(x)))^2)/n)

The formula is used when all of the values in the population are known. If the values x1...xn are a random sample chosen from the population, then the sample Standard Deviation is calculated with same formula, except that (n-1) is used as the denominator.

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["Barrons Dictionary of Mathematical Terms, second edition"].
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## standard deviation

In statistics, the average amount a number varies from the average number in a series of numbers.
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References in periodicals archive ?
STD DEV = Three-year annualized standard deviation;
Table 1 CASES CONTROLS MEAN STD DEV MEAN STD DEV p value * RHI 1.74 0.418 1.61 0.380 0.411 AI 29.4% 26.6% 19.7% 22.4% 0.327 * Independent samples, t-test Table 2.
Check the appropriate Mean Std Dev level of difference between these two groups Willingness to participate in 1.39 0.63 programs/ services Client's motivation to improve their 1.40 0.67 well being through Services.
The 2 standard deviation (STD Dev) range was 0.3 to 2.4g/Lcreatinine.For children under 12 years of age, the statistical evaluation showed a mean value of 0.9g/L creatinine.
E' (MPa) E' (MPa) Treatment/ Temperature NA TA MA NA 7510 after 1 cycle after 300 cycles 30[degrees]C (ave) 1584 2034 1908 1606 (std dev) (216) (150) (99) (187) 60[degrees]C (ave) 606 728 675 532 (std dev) (59) (60) (35) (13) 7110 after 1 cycle at failure 60[degrees]C (ave) 1477 1650 1524 1214 (std dev) (162) (195) -- (169) 90[degrees]C (ave) 516 652 -- 233 (std dev) (15) (91) -- (86) E' (MPa) Treatment/ Temperature TA MA 7510 30[degrees]C (ave) 2069 1859 (std dev) (110) (93) 60[degrees]C (ave) 674 551 (std dev) (54) (31) 7110 60[degrees]C (ave) 1465 1240 (std dev) (18) -- 90[degrees]C (ave) 354 -- (std dev) (46) -- Table 5 Stress Intensity Factors ([K.sub.q]) From CT Tests.
Adoption Scale by Cluster ADOPTSCALE Cluster 1 Cluster 2 Cluster 3 Cluster 4 F statistic (N = 39) (N = 135) (N = 203) (N = 208) (p value) Mean 0.59 4.46 6.33 9.48 329.608 Std Dev 0.88 2.33 1.78 1.98 0.000 Table 4.
These parameters are proportion of contamination (% CONTAM), mean shift (MEAN SHIFT) and standard deviation of [P.sub.c] (STD DEV [P.sub.c]).
of AR Cat days 599 484 Avg duration (h) 13.3 21.0 Std dev duration (h) 4.7 9.5 Avg max IVT (kg [m.sup.-1] [s.sup.-1]) 373.7 480.0 Std dev max IVT (kg [m.sup.-1] [s.sup.-1]) 62.4 108.6 Avg storm-total IVT ([10.sup.7] kg [m.sup.-1]) 1.6 2.8 Std dev storm-total IVT ([10.sup.7] kg [m.sup.-1]) 1.2 I.I Avg 3-day IVT ([10.sup.7] kg [m.sup.-1]) (a) 4.9 5.7 Std dev 3-day IVT ([10.sup.7] kg [m.sup.-1]) (a) 0.4 1.5 Characteristic Cat 2 Cat 3 No.
Cp (or Pp) = Spec range / (6 x total system variation (std dev)).

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