Z Score

z-score is the number of standard deviations from the mean a data point is. But more technically it’s a measure of how many standard deviations below or above the population mean a raw score is.

Standard scores give you a way of comparing values across different sets of data where the mean and standard deviation differ

.They’re a way of comparing related data values in different circumstances. As an example, you can use standard scores to compare each player’s performance relative to his personal track record—a bit like a personal trainer would.

You find the standard score of a particular value using the mean and standard deviation of the entire data set. The standard score is normally denoted by the letter z, and to find the standard score of a particular value x, you use the formula:

Let’s calculate the standard scores for each player, and see what those scores tell us.