In the context of measurement scales, what distinguishes a ratio scale from an interval scale?

A ratio scale is distinguished from an interval scale primarily by the presence of a true-zero point. In a ratio scale, zero indicates the absence of the quantity being measured. For example, in a weight measurement, zero grams means there is no weight present. This allows for meaningful comparisons between measurements, such as saying that 10 kilograms is twice as heavy as 5 kilograms.

On the other hand, an interval scale does not have a true zero; instead, it has a zero point that does not indicate the absence of the quantity. For instance, in temperature measured in Celsius, 0 degrees does not mean a complete lack of temperature, but rather a position on the scale.

While ordered ranks and equally spaced values are characteristics of both scales, they do not define the key difference between ratio and interval scales. Similarly, arbitrary categories pertain more specifically to nominal scales and do not apply in this context. The critical aspect that sets the ratio scale apart is its true zero point, which allows for meaningful ratios and comparisons in measurement.