# Standard Deviations

### Some articles on standard deviation, standard deviations, deviation, deviations:

Reference Range - Standard Definition - Establishment Methods - Log-normal Distribution
... right, this phenomenon has relatively small effect if the standard deviation (as compared to the mean) is relatively small, as it makes the log-normal ... Thus, the arithmetical normal distribution may be more appropriate to use with small standard deviations for convenience, and the log-normal distribution with large standard deviations ... In a log-normal distribution, the geometric standard deviations and geometric mean more accurately estimate the 95% prediction interval than their arithmetic counterparts ...
Sample Standard Deviation - Interpretation and Application - Rules For Normally Distributed Data
... random variables, σ equals their distribution's standard deviation divided by n1/2, and n is the number of random variables ... The standard deviation therefore is simply a scaling variable that adjusts how broad the curve will be, though it also appears in the normalizing ... distribution is approximately normal, then the proportion of data values within z standard deviations of the mean is defined by Proportion = where ...
Correlation And Dependence - Pearson's Product-moment Coefficient
... It is obtained by dividing the covariance of the two variables by the product of their standard deviations ... random variables X and Y with expected values μX and μY and standard deviations σX and σY is defined as where E is the expected value operator, cov ... correlation is defined only if both of the standard deviations are finite and both of them are nonzero ...
68-95-99.7 Rule - Uses
... to quickly get a rough probability estimate of something, given its standard deviation, if the population is assumed normal, thus also as a simple test for outliers (if the population ... Recall that to pass from a sample to a number of standard deviations, one computes the deviation, either the error or residual (accordingly if one knows the ... or a normality test, one computes the size of deviations in terms of standard deviations, and compares this to expected frequency ...
List Of Six Sigma Software Packages - Origin and Meaning of The Term "six Sigma Process"
... The term "six sigma process" comes from the notion that if one has six standard deviations between the process mean and the nearest specification limit, as shown in the graph, practically no items will fail to meet ... Capability studies measure the number of standard deviations between the process mean and the nearest specification limit in sigma units ... As process standard deviation goes up, or the mean of the process moves away from the center of the tolerance, fewer standard deviations will fit between the mean and the nearest specification limit ...

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