By measurement, we usually mean the assigning
of number to observations or objects and scaling is a process of measuring.
The four
scales of measurements
NOMINAL
SCALE
The classification
or grouping of the observations into mutually exclusive qualitative categories
or classes is said to constitute a nominal
scale.
For example, students are classified as male and female. Number 1 and 2 may
also be used to identify these two categories. The numbers
when they are used only to identify the categories of the given scale, and
there
is no particular order for the grouping.
ORDINAL OR
RANKING SCALE
It
includes
the characteristic of a nominal scale and in addition
has the
property of ordering
or ranking of
measurements. For example,
the performance of students (or players) is rated as
excellent,
good fair or poor, etc. Number 1, 2, 3, 4 etc. are also
used
to indicate ranks. The only relation that holds between
any
pair of categories is that of “greater than” (or more preferred).
INTERVAL
SCALE
A measurement
scale possessing a constant interval size (distance) but not a true zero point,
is called an interval scale.
Temperature measured on either the Celsius
or
the Fahrenheit scale is an outstanding example of interval scale because the
same difference exists between 20o C (68o F) and 30o C (86o F) as between 5o C
(41o F) and 15o C (59o F).
RATIO
SCALE
It is a
special kind of an interval scale where the sale of measurement has a true zero point as its origin. The ratio
scale is used to measure weight, volume, distance, money, etc. The, key to
differentiating interval and ratio scale is that the zero point is meaningful
for ratio scale.
⇛ Statistics Part 3.
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