Z-value

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Z-value

(in statistics) indicates how many STANDARD DEVIATIONS away from the MEAN a value resides. For a given set of data the mean (x) is subtracted from each member (x) of the set; then each member is divided by the standard deviation (s) of the set: z = (x - x)/s. A positive score indicates the value is above the mean, a negative score indicates below. Z-values are useful in comparing sets of data with different means and standard deviations.