z-score

Z-score is measured in terms of standard deviations from the mean.

\(z=\dfrac{\text{data point}-\text{mean}}{\text{standard deviation}}\)
in short
\(z=\dfrac{x-\mu}{\sigma}\)
How to describe z-score
Michael’s z-score is  0.5. His grade was half of a standard deviation above the mean.
Michael’s z-score is  -2. His grade was two standard deviations below the mean.