The standard deviation of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 is approximately 2.87. So, if you're into numbers, that's the magic number you're looking for. But hey, don't stress about it too much, just know that's the spread of those digits.
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z=(x-mu)/s = (-10+9)/2 z = -1/2 Note that the standard normal has a mean of 0, therefore: The value of -10 is to the left of the mean of -9 The value of -1/2 is to the left of the mean of 0.
http://www.hedgefund.net/pertraconline/statbody.cfmStandard Deviation -Standard Deviation measures the dispersal or uncertainty in a random variable (in this case, investment returns). It measures the degree of variation of returns around the mean (average) return. The higher the volatility of the investment returns, the higher the standard deviation will be. For this reason, standard deviation is often used as a measure of investment risk. Where R I = Return for period I Where M R = Mean of return set R Where N = Number of Periods N M R = ( S R I ) ¸ N I=1 N Standard Deviation = ( S ( R I - M R ) 2 ¸ (N - 1) ) ½ I = 1Annualized Standard DeviationAnnualized Standard Deviation = Monthly Standard Deviation ´ ( 12 ) ½ Annualized Standard Deviation *= Quarterly Standard Deviation ´ ( 4 ) ½ * Quarterly Data
Standard deviation is the square root of the variance. Since you stated the variance is 4, the standard deviation is 2.
The formula for standard deviation has both a square (which is a power of 2) and a square-root (a power of 1/2). Both must be there to balance each other, to keep the standard deviation value's magnitude similar to (having the same units as) the sample numbers from which it's calculated. If either is removed from the formula, the resulting standard deviation value will have different units, reducing its usefulness as a meaningful statistic.
From the online calculator, see related link, the standard deviation is 4.06202.