Which level of measurement corresponds to equal changes in the variable for each unit on a scale?

Which level of measurement corresponds to equal changes in the variable for each unit on a scale?

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

Answer: (C)

Equal steps between adjacent values define an interval scale. This means the distance from one point to the next is the same everywhere on the scale, so differences are meaningful—like the difference between 20 and 30 being the same as between 70 and 80. However, the zero on an interval scale is arbitrary, so you can’t reliably interpret ratios (for example, 60 is not "twice" 30). That combination of equal spacing with an arbitrary zero is what characterizes interval measurement. Nominal scales have categories without order, and ordinal scales have order but not guaranteed equal distances between points.

Equal steps between adjacent values define an interval scale. This means the distance from one point to the next is the same everywhere on the scale, so differences are meaningful—like the difference between 20 and 30 being the same as between 70 and 80. However, the zero on an interval scale is arbitrary, so you can’t reliably interpret ratios (for example, 60 is not "twice" 30). That combination of equal spacing with an arbitrary zero is what characterizes interval measurement. Nominal scales have categories without order, and ordinal scales have order but not guaranteed equal distances between points.