If the distribution of test scores is skewed, which statistics are preferred to summarize central tendency and spread?

• A. Mean and standard deviation
• B. Median and interquartile range
• C. Mode and range
• D. Mean and range

Answer: (B)

When data are skewed, use a measure that isn’t pulled by extreme values. The median serves as a robust center because it reflects the middle point of the data regardless of how far the tails extend. The interquartile range focuses on the spread of the central 50% of scores, ignoring the extremes and giving a stable sense of variability.

Mean and standard deviation, in contrast, are sensitive to outliers and the long tail of a skewed distribution, which can distort both the typical score and the perceived spread. The range depends entirely on the extreme values and can be heavily influenced by a single outlier, making it less reliable. The mode isn’t consistently informative for central tendency in many datasets, and it doesn’t capture spread well.