How many standard deviations a value is from the mean.
In this example, the value 1.7 is 2 standard deviations away from the mean of 1.4, so 1.7 has a z-score of 2.
Similarly 1.85 has a z-score of 3.
So to convert a value to a Standard Score ("z-score"):
· first subtract the mean,
· then divide by the standard deviation