The standard deviation would be an appropriate measure of variability only if the variable is measured on:

A) nominal and ratio scales.
B) ordinal and nominal scales.
C) interval and ratio scales.
D) optimal and interval scales.

Measure Variability

The extent to which data points in a set diverge from the average value, indicating the spread or dispersion in the data.

Interval Scales

A type of scale used in measurement that involves numerical values where the intervals between values are interpretable, but there's no true zero point.

Variable

A variable is any characteristic, number, or quantity that can be measured or counted.