In the context of z-scores, which distribution is the reference for interpreting z-scores?

• A. Normal distribution
• B. Skewed distribution
• C. Uniform distribution
• D. Bimodal distribution

Answer: (A)

Z-scores express how far a value lies from the mean, measured in units of standard deviation. To interpret them, we use the standard normal distribution—the bell-shaped curve with a mean of 0 and a standard deviation of 1. This reference provides the probabilities and percentiles that correspond to each z-score, so any score can be placed on a common scale and compared across different measures. If the underlying data are not normally distributed, the z-score is still a standardization, but the probabilities you’d look up on the standard normal curve may not accurately reflect the data’s actual distribution. Other distribution shapes—skewed, uniform, or bimodal—don’t provide the same symmetric, well-defined probability structure that the standard normal curve offers, so they aren’t used as the reference for interpreting z-scores.