What kind of measurement scale is necessary to conclude that one score is twice as big as another?

• A. Ordinal
• B. Interval
• C. Ratio
• D. Interval or ratio

Answer: (C)

This question hinges on understanding which measurement scale allows meaningful ratios between scores. To say that one score is twice as big as another, you need a scale with a true zero point, where zero really means “none of the attribute.” That is the ratio scale.

On an ordinal scale you only know which score is bigger, not how much bigger; you can’t compare magnitudes or claim doubling. An interval scale gives you equal-sized units, but the zero point is arbitrary, so ratios aren’t meaningful (for example, 20 degrees is not necessarily twice 10 degrees in a way that holds across contexts). Without a true zero, saying one score is twice another can be misleading.

With a ratio scale, zero denotes the absence of the attribute, and you can legitimately say that one score is exactly twice another (for instance, weights or counts). Therefore, the necessary measurement scale is ratio.