and absolute zero.
Nominal Scale
The nominal scale involves just naming or classifying things. This can be
specific categories. For example people can be labelled as male or female.
Many other things such as blood groups, games and foods can be labelled in
this way. An alternative form of labelling is that there is some condition quality
or characteristic that is either present or absent. Thus a person is either dead
or alive, or they do or do not have a certain disease.
There are two distinguishing features of the nominal scale. First, once
something is assigned to a category, for example, male or female, apple or
orange, there is no further description. Second, strictly it is not a measurement
scale at all. While it is possible to designate classes of things by a number, the
number is used as a label not a value.
Ordinal Scale
The ordinal scale, also called the ranking scale, has the property called
magnitude as well as classification. It provides ordinal measurement.
Magnitude gives items an order, ranking or place. An example is the places in a
horse race. These numbers, however, only assign a place. They do not
otherwise measure performance. For example, in a horse race a horse still
comes second no matter what the margin is between it and the horse that
comes first. As the saying goes, an inch is as good as a mile. In formal
language this is saying that with the ordinal scale, there are not equal scales
between rankings.
Interval Scale
The interval scale provides both cardinal and ordinal measurement. Obviously
it provides cardinal measurement according to the interval scale, which also
classifies the item that is measured. The interval scale has two distinguishing
properties. First, there are equal intervals on the scale as the name indicates.
No
matter where something is on the scale, the next interval up or down is
always the same magnitude away. Examples of the interval scale are the
Celsius and Fahrenheit temperature scales. Second, an interval scale does not
have absolute zero (and this is how it is distinguished from the ratio scale).
This is why 40 degrees is not twice as hot as 20 degrees, which would be the
case if the scale had absolute zero.
Because the interval scale provides a form of cardinal measurement it also
furnishes ordinal measurement. It orders the items according to their cardinal
value.
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