What defines an interval variable in measurement?

An interval variable is characterized by having both order and meaningful differences between values, which makes it possible to determine how much one value differs from another. This means that you can quantify the differences between measurements. For instance, in temperature measured in degrees Celsius or Fahrenheit, the difference between 20 degrees and 30 degrees is the same as the difference between 80 degrees and 90 degrees.

While the other options reference important concepts relating to measurement—such as the definition of zero or the ability to have ratios—they are not accurate descriptions of interval variables. Interval variables do not have an absolute zero that signifies the complete absence of the quantity being measured; rather, they have a point that is arbitrarily defined as zero. Additionally, the concept of meaningful ratios applies more to ratio variables, not interval variables, as ratio variables include a true zero that reflects an absence of the variable. Therefore, the defining characteristic of interval variables is their ordered nature and the meaningful differences that exist between values.