Nominal – this is the lowest level of measurement and
usually associated with qualitative data.
Examples of this type of data include political affiliation, eye color,
type of fruit, brand of running shoe, etc.
Nominal data is divided into categories.
The categories are the ‘units’ of the scale and the items are ‘measured’
by determining which category they belong to.
Measuring items using a nominal scale is the equivalent of classifying
the items to the category in which they belong.
When using nominal data, there is no magnitude relationship between the
units of the scales; an apple is no more or less of a fruit than a pear is.
Ordinal – ordinal data is the next highest level of
measurement. Ordinal scales rank order
the items that are being measured to indicate if they possess more, less, or
the same amount of the variable being measured.
An ordinal scale allows us to determine if X > Y, Y > X, or if X =
Y. An example would be rank ordering the
participants in a dance contest. The
dancer who was ranked one was a better dancer than the dancer who was ranked
two. The dancer ranked two was a better
dancer than the dancer who was ranked three, and so on. Although this scale allows us to determine
greater than, less than, or equal to, it still does not define the magnitude of
the relationship between units. Dancer
one might be much better than dance two but dancer two might be only slightly
better than dancer three; the data does not answer that question. Likert scale data is also a common example of
ordinal data.
Scale – this type of data possess the properties of
magnitude and equal interval between adjacent units. Equal intervals between adjacent units means
that there are equal amounts of the variable being measured between adjacent
units on the scale. An example would be
age. An increase in age from 21 to 22
would be the same as an increase in age from 60 to 61; one year. In addition, we can perform mathematical
functions on scale data to determine if X - Y = A - B, X – Y > A – B, or if
X – Y < A – B. We can also perform other mathematical
operations including addition, multiplication, and division.
