The interval scale is a
type of measurement
scale where the interval between
successive points can be measured using
a defined numerical scale, however the zero
point does not indicate absence of the characteristic
being measured, but is arbitrary or undefined.
Calendar time and temperature, in degrees
centigrade, are examples of interval scales.
Examples of interval scales are fairly
rare, but it is important to recognize them
because some mathematical operations, including
multiplication and division, are not valid
for interval scales.
A scale that has the characteristics of
an interval scale, but also zero does indicate
the absence of the characteristic being
measured (eg. length, weight) is known as