NCIt definition : A method for converting an individual score into a standard form. The z-score indicates
how far and in what direction an item deviates from its distribution's mean, expressed
in units of standard deviation. Calculation of a z-score requires knowledge about
the population's standard deviation and mean.;
Alternative definition : CDISC: The number of positive or negative standard deviations of a measured value
from the mean of its population.;