Which four measures are commonly used to describe a data set's central tendency and spread?

• A. Mean, median, and standard deviation
• B. Median, mode, and interquartile range
• C. Mean, median, mode, and range
• D. Mean, median, and standard deviation

Answer: (C)

Describing a data set involves two ideas: where the data tend to cluster (central tendency) and how far apart the values are (spread). The typical values are captured by mean, median, and mode. A simple measure of spread is the range, which is the difference between the largest and smallest value. Using all four—mean, median, mode, and range—gives a clear picture of both the center and the spread of the data. The other options mix in different spread ideas or miss one of the central measures and therefore don’t provide the complete four-measure summary. For example, in a small set like 1, 2, 2, 3, 9, the mean is 3.4, the median is 2, the mode is 2, and the range is 8. That combination best describes both where the data sit and how spread out they are.