ABSTRACT
Also termed ‘standard Normal deviate’. A z-score is a measurement from a Normal distribution that is expressed in units of standard deviation (SD), and not in the original units of the measurement. For example, if the mean height for a group of people is 172 cm with SD equal to 10 cm, a person measuring 182 cm has a z-score of 1 (i.e. is +1 SD away from the mean). z-scores are obtained through a linear transformation, by subtracting the mean from the individual measurements, and dividing the result by the SD. Thus, measurements are converted into a Normal distribution with mean = 0 and SD = 1 (i.e. the standard Normal distribution):
