zscores are one of the common measures of relative position; they describe the location of a value relative to the mean.
Recall that standardization converts data values into correspondingzscores. Here, the mean always has a zerozscore.
Azscore of 1 indicates that a data value is one standard deviation above the mean, while minus 2 suggests two standard deviations below the mean.
The ordinary, or majority, of values in any distribution lie within thezscore of minus 2 to plus 2. Any values beyond this range are considered unusual, or outliers, and are considered far away from the other data values. Outliers may indicate variabilities in measurement or experimental errors.
For example, a student’s height has a plus 3.3zscore, or 3.3 standard deviations away from the class average, indicating that she is unusually tall for her class.
