# Interval Scale

An Interval Scale is ...

**Context:**- It is associated with an Affine Space.
- It is associated with a Scaled Variable (Interval Variable).

**See:**Interval; Scale; Ordinal Scale; Ratio Measurement.

## References

### 2011

- (Sammut & Webb, 2011) ⇒ Claude Sammut, and Geoffrey I. Webb. (2011). “Interval Scale.” In: (Sammut & Webb, 2011) p.553
- (Wikipedia, 2009) ⇒ http://en.wikipedia.org/wiki/Level_of_measurement#Interval_scale
- Quantitive attributes are all able to be measured on interval scales, as any difference between the levels of an attribute can be multiplied by any real number to exceed or equal another difference. A highly familiar example of interval scale measurement is temperature with the Celsius scale. In this particular scale, the unit of measurement is 1/100 of the difference between the melting temperature and the boiling temperature of water in atmospheric pressure. The "zero point" on an interval scale is arbitrary; and negative values can be used. The formal mathematical term is an affine space (in this case an affine line). Variables measured at the interval level are called "interval variables" or sometimes "scaled variables" as they have units of measurement.
- Ratios between numbers on the scale are not meaningful, so operations such as multiplication and division cannot be carried out directly. But ratios of differences can be expressed; for example, one difference can be twice another.