Which statement is true about interval and ratio measurement scales?

• A. Ratio scales have a true zero, and interval scales do not.
• B. Interval scales have a true zero, ratio scales do not.
• C. Both have a true zero, but only ratio allows meaningful ratios.
• D. Interval scales are qualitative, ratio are qualitative as well.

Answer: (A)

The main distinction between interval and ratio scales is whether there is a true zero and what that allows you to say about the numbers. A true zero means the zero point truly indicates the absence of the quantity. On a ratio scale, this is the case, so you can form meaningful ratios. For example, weight or length: 20 kg is twice as heavy as 10 kg, and 0 kg means no weight at all.

Interval scales have equal units and equal intervals, but their zero point is arbitrary. Temperature on the Celsius or Fahrenheit scales is a classic example: 0 does not mean there is no temperature, and you cannot reliably say that 20°C is twice as hot as 10°C. That’s why you can compare differences (20°C − 10°C = 10°C) but not ratios.

This is why the statement is true: ratio scales have a true zero, and interval scales do not. The other options misstate these properties or ignore the quantitative nature of these scales.