Which of the following is an example of a ratio scale?

• A. Pain intensity on a 0-10 scale
• B. Temperature measured in Celsius
• C. A qualitative yes/no response
• D. Time to complete a task

Answer: (D)

Ratio scales have a true zero point and equal intervals between values, which lets you compare both differences and ratios meaningfully. Time to complete a task fits this perfectly: zero represents no time elapsed, and each unit of time (seconds, minutes, etc.) is equally spaced, so you can say one task took twice as long as another. In contrast, the pain intensity scale is typically treated as ordinal—numbers indicate more pain, but the steps between them aren’t guaranteed to be equal, and zero pain isn’t necessarily a true mathematical absence in the same way. Temperature in Celsius is interval: zero is arbitrary (it doesn’t mean no temperature), so ratios like twice as hot aren’t meaningful. A qualitative yes/no response is nominal, with categories that have no inherent order or measurable distance between them.