Which of the following is an example of ratio data?

Ratio data is characterized by having a true zero point and allowing for the comparison of magnitudes. This means that not only can you determine the difference between values, but you can also say how many times greater one value is compared to another.

In the context of the question, range of motion (ROM) is indeed an example of ratio data because it can be measured in degrees, where zero degrees represents the complete absence of movement (true zero). Additionally, if one person has a ROM of 30 degrees and another has a ROM of 60 degrees, you can say that the second person's ROM is twice as much as the first's.

The other options do not possess these characteristics. For example, handiness is often categorized as a nominal variable, indicating whether a person is right-handed or left-handed, without a meaningful way to measure or compare in terms of magnitude. The pain rating scale typically uses ordinal data, where the values indicate ranks but do not maintain equal intervals or a true zero. Finally, scores on a standardized assessment usually represent ordinal or interval data that do not possess a true zero, as the scores signify performance rather than a physical measurement experiencing magnitude comparisons.