What Are Negative Z Scores?

For example, a Z score of -1 shows that the value is one standard deviation below the group mean value. If data are normally distributed, 95 percent of Z scores will fall between -2 and 2 and are considered typical values that represent the sample well. Z scores help statisticians more quickly assess whether a score is typical and aid in the comparison of individual scores from different groups of data. Z scores are also called standardized scores.