The standard deviation is a basic measure of the "scatteredness" of data and it applies to the entire data set.

The z-score is a measure of how many standard deviations away from the mean a raw datum is and it applies to individual values.

Thus the two are not the same. The standard deviation of the data set must be computed before the z-score of each value can be determined.

The z-score is a measure of how many standard deviations away from the mean a raw datum is and it applies to individual values.

Thus the two are not the same. The standard deviation of the data set must be computed before the z-score of each value can be determined.