Standard Deviation can be described as which of the following?

• A. The square root of the variance
• B. A measure of distribution around the mean
• C. The difference between the lowest and highest score
• D. None of the above

Answer: (A)

Standard deviation is a measure of how spread out data are around the mean, and its precise mathematical definition is the square root of the variance. The variance itself is the average of the squared differences from the mean, which captures dispersion but lands in squared units. Taking the square root returns the measure to the original units of the data, giving a directly interpretable gauge of typical deviation from the mean. That specific definition—the square root of the variance—is why this answer is the best choice. Saying it’s simply a measure of distribution around the mean describes its role, but does not give the exact formula. The idea of the range, the difference between the lowest and highest score, misses how values are distributed in between and is not the standard deviation. So the square root of the variance is the correct description.