Source: wikihow.com

A Z score allows you to take any given sample within a set of data and to determine how many standard deviations above or below the mean it is. To find the Z score of a sample, you’ll need to find the standard deviation and mean of a set of data, find the difference between a value in the sample and the mean, and divide it by the standard deviation. If you follow these steps, you’ll see that calculating the Z score isn’t as tricky as it sounds.