Standard Error of the Mean

The standard error of the mean is an estimate of the standard deviation of means that would be found if many samples of n items were repeatedly collected from the same population.

An alternate description: Suppose many samples of size n were repeatedly collected from the same population and the means of these many samples were calculated. The means of the samples would themselves form a data set. The standard error of the mean is an estimate of the standard deviation of this theoretical sample of means.

Standard Error of the Mean (SE)

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where

S	= Sample Standard Deviation
n	= number of data values for a sample