Which of the following describes a ratio scale?

A ratio scale is characterized by the presence of a true zero point, allowing for not only the measurement of differences between values but also the calculation of ratios. This means that on a ratio scale, one can say that something is "twice as much" as another, making it possible to conduct a full range of statistical analyses, including those that require dimensionality and comparison, such as multiplication and division.

The option regarding the numerical scale supporting a full variety of statistical analyses is correct because ratio scales provide the highest level of measurement precision and flexibility. They facilitate a depth of statistical manipulation not available with nominal or ordinal scales, which only permit limited analyses, or interval scales, which lack a true zero.

The other options discuss characteristics of other types of scales or measurement systems rather than accurately defining a ratio scale. A true zero point is essential for a ratio scale, so the option indicating that a scale lacks this quality cannot apply. Similarly, the ability to measure only differences refers to interval scales, which do not measure ratios. Lastly, a qualitative measure is not compatible with the defined characteristics of a ratio scale, which is inherently quantitative.