What does a Z-score represent?

• A. Number of standard deviations above average
• B. Number of standard deviations below average
• C. Difference from the mean in raw scores
• D. Ratio of scores to averages

Answer: (B)

A Z-score is a statistical measurement that indicates the position of a value in relation to the mean of a group of values, specifically expressed in terms of standard deviations. When interpreting a Z-score, it tells us how many standard deviations a given score is above or below the mean of the dataset.

In this context, a Z-score can be positive, indicating the score is above the mean, or negative, indicating it's below the mean. However, the specific option selected correctly captures that a Z-score quantifies a score's deviation from the average.

Choosing this indicates an understanding that a Z-score does not merely represent the number of standard deviations – it articulates the direction of that deviation (above or below). This understanding is essential in contexts such as bone densitometry, where knowing how a specific measurement compares to the average can inform clinical decisions regarding bone health and the risk of conditions like osteoporosis.