Z-scores are expressed in what kind of units?

• A. In standard deviation units.
• B. In raw data units.
• C. In probabilities.
• D. In percentages of the mean.

Answer: (A)

Z-scores express how far a value lies from the mean in terms of standard deviations. You compute a z-score by subtracting the mean and dividing by the standard deviation, so it shows how many standard deviation units the observation is above or below the mean. For example, a z-score of 1 means one standard deviation above the mean, while a z-score of -2 means two standard deviations below. This standardization lets you compare values from different distributions on the same scale. The other options don’t fit: raw data units keep the original measurement scale, probabilities aren’t the z-score itself (they come from looking up the area under the normal curve), and percentages of the mean aren’t what a z-score represents.