Interval vs ratio scale zero – UGC NET Question

A ratio scale possesses all the properties of an interval scale—equal units and meaningful differences—plus a true zero point that indicates the complete absence of the quantity being measured. Because of the true zero, statements such as one value being twice another are meaningful. Examples include height, weight and Kelvin temperature. Thus, a scale with equal units and a true zero that allows ratio comparisons is correctly called a ratio scale.

Option A:
Nominal scales classify objects into categories without any inherent order, such as gender or blood group. They do not have equal units or a zero point with quantitative meaning, so they do not match the stem.

Option B:
Ordinal scales rank order items but do not guarantee equal intervals between ranks; they allow comparison of “greater than” or “less than” but not meaningful differences or ratios. Hence, ordinal is not the right answer.

Option C:
Interval scales have equal units and allow meaningful differences to be calculated, but they lack a true zero, so ratios can be misleading. Celsius temperature is a classic example. Therefore, interval does not fulfil the true-zero condition in the stem.

Option D:
Option D, ratio scale, uniquely combines equal intervals with an absolute zero, enabling multiplication and division operations that are not valid on other scales. This matches the description in the question precisely.