The measurement scale must be interval or ratio for the difference of 4 points to be meaningful. This is an example of which option?

The measurement scale must be interval or ratio for the difference of 4 points to be meaningful. This is an example of which option?

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

Answer: (D)

A meaningful difference between scores only makes sense when the scale has equal units. On nominal scales, numbers just label categories with no notion of distance. On ordinal scales you know which score is higher, but you can’t assume the steps between levels are equal, so a difference of four points would be arbitrary. On interval scales the units are evenly spaced, so subtracting two scores to get a difference is meaningful. On ratio scales you also have a true zero, so both differences and ratios are interpretable. Since a difference of four points is meaningful only when the scale is interval or ratio, the best-fit option is Interval or Ratio.

A meaningful difference between scores only makes sense when the scale has equal units. On nominal scales, numbers just label categories with no notion of distance. On ordinal scales you know which score is higher, but you can’t assume the steps between levels are equal, so a difference of four points would be arbitrary. On interval scales the units are evenly spaced, so subtracting two scores to get a difference is meaningful. On ratio scales you also have a true zero, so both differences and ratios are interpretable. Since a difference of four points is meaningful only when the scale is interval or ratio, the best-fit option is Interval or Ratio.