What defines a ratio variable?

A ratio variable is characterized by its numerical nature and the presence of a true zero point, which indicates the absence of the quantity being measured. This true zero allows for meaningful comparisons between values, enabling both the calculation of ratios and the application of mathematical operations such as addition, subtraction, multiplication, and division.

For instance, in the case of length, a measurement of zero meters indicates there is no length at all, while a measurement of four meters can be interpreted as being twice as long as two meters. This property is what differentiates ratio variables from other types of variables, such as interval variables, which may lack a true zero (for example, temperature measured in Celsius).

The other types of data mentioned in the options clarify what ratio variables are not. Categorical data with rank refers to ordinal data, where the values convey a ranking but do not have measurable distances between ranks. Numerical data without a true zero could refer to interval data; while they might exhibit numerical relationships, the lack of a true zero means we cannot say one value is a multiple of another. Data lacking inherent rank would refer to nominal data, which consists of categories with no specific ordering.

Therefore, the essential aspect that defines a ratio variable is that it consists of numerical data,