Measurement Scales

⇛ Statistics Part 1.

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 orderingor 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.