Which data type is defined by numeric scales with equal intervals between values?

• A. Nominal data scale
• B. Ordinal data
• C. Percentile range
• D. Interval data

Answer: (D)

Numeric scales with equal steps between consecutive values define interval data. This means the distance between values is consistent, so differences are meaningful and you can perform arithmetic like calculating means, standard deviations, and comparing how large one change is relative to another. For example, on the Celsius temperature scale, the difference between 10°C and 20°C is the same 10-degree change as between 20°C and 30°C. However, the zero on this scale is arbitrary, so ratios aren’t meaningful—20°C isn’t twice 10°C.

Nominal data are just category labels with no inherent order (like colors), while ordinal data have order but unequal intervals (like a 1–5 rating where the steps aren’t equal). Percentile range isn’t a data type scale itself; it describes a position within a distribution.