<prompt> The measure of variability indicating how many standard detions, an observation is above or below the mean isZ scoreStandard error S.EStandard detion S.DCo-efficient of Variation  <response>: A z-score is the number of standard detions from the mean. The coefficient of variation CV is a measure of relative variability. It is the ratio of the standard detion to the mean. Ref : Park 23rd edition Pgno : 849 