The z-score of a data value reflects how far away from the mean an individual data point is, in units based off of the standard deviation. For instance, if a data point has a z-score of 1, it is 1 full standard deviation away from the mean. The sign of the z-score relays whether the score is larger or smaller than the mean, with negative scores being smaller and positive scores being larger. Like relative standard deviation, z-scores are useful for comparing data between different sets.