In statistics, what does the standard deviation measure?

• A. The dispersion of data from the mean
• B. Central tendency
• C. Correlation
• D. Data frequency

Answer: (A)

Standard deviation measures how spread out the data are around the average value. It captures the variability or dispersion: a small standard deviation means most observations are close to the mean, while a large one indicates more spread with values farther from the mean. It’s calculated by averaging the squared differences from the mean and then taking the square root, which keeps the units consistent with the data.

This is not about where the data tend to sit overall (central tendency), which is described by the mean or median. It also doesn’t describe the relationship between two variables (that’s correlation) or how often values occur (data frequency).