Which type of data includes a true zero and allows for comparison by ratios?

The type of data that includes a true zero and allows for comparisons by ratios is known as ratio data. This classification is part of a hierarchy of data types that also includes nominal, ordinal, and interval data.

In ratio data, the presence of a true zero point indicates that the absence of a quantity is meaningful. For instance, in a measurement of weight, a value of zero means there is no weight at all. This allows for meaningful calculations, such as determining that 10 kg is twice as heavy as 5 kg. Because of this true zero, ratio data permits a full range of mathematical operations, including addition, subtraction, multiplication, and division.

In contrast, nominal data categorizes items without any quantitative value, ordinal data provides rankings but does not assume equal intervals between ranks, and interval data consists of ordered values with equal distances between them but lacks a true zero point. Thus, only ratio data provides the capability to make comparisons based on ratios, reinforcing its unique position in the hierarchy of data types.