Which scale or scales of measurement have an absolute zero point?

Concept

Measurement scales differ in the operations their values support. An absolute or true zero represents the complete absence of the measured quantity, so ratios such as “twice as much” become meaningful.

Nominal and ordinal scales organize categories, while interval and ratio scales support equal numerical differences. Their treatment of zero distinguishes the latter two.

Application

Apply the defining properties of each scale to the requirement of an absolute zero:

1. Nominal labels categories; a numerical code such as 0 is only a label.

2. Ordinal ranks categories; its positions do not require equal intervals or a true zero.

3. Interval uses equal units, but its zero is an arbitrary reference point, as in degrees Celsius.

4. Ratio uses equal units and a true zero, so both differences and ratios are meaningful.

Contrast

• Nominal and ordinal do not define zero as absence of the measured quantity.

• Interval and ratio share equal intervals, but only one of them uses a non-arbitrary zero.

Cross-check

Celsius temperature is interval-scaled because 0 °C does not mean no temperature; Kelvin temperature is ratio-scaled because 0 K is absolute zero. This confirms the zero-point distinction.

Result

Therefore, the ratio scale alone has an absolute zero point.