A numerical characteristic of interest in each element of the sample.

• A. Observations
• B. Data set
• C. Univariate data
• D. Variable (statistics)

Answer: (D)

A variable is a property that can take different values across elements of the sample, and when that property is numerical, it’s a quantitative variable. The statement points to the thing we measure for each unit in the sample—the numerical characteristic of interest. For example, if you record the height of every student in a class, height is the variable. The actual numbers you collect are the values of that variable across observations. The collection of those values forms the data set, and each student is an observation. If you have measurements on a single variable, the data are univariate, but the essential idea here is that the variable is the numerical characteristic you study for each element.