Definition: The Scales of Measurement are used to quantify or categorize the variables and before any research one must identify the type of the variable under study. As different methods are used to measure different variables.
The numbers or set of numbers assigned to the object has certain specific qualities that interest the researcher. These qualities are magnitude, equal intervals and absolute zero, which helps in determining the type of measurement scale to be used and the best statistical method to be applied.
The Magnitude means the ability to determine the degree to which one score is less than, or greater than another score. The Equal Interval means an equal distance each possible score has from each other. The Absolute Zero is a point where a score of zero can be assigned, or none of the scale exists. These scale qualities collectively determine the four scales of measurement. These are:
- Nominal Scale: The nominal scale is a scale which represents only the names or where the numbers serve only as labels or tags to categorize or identify the objects. This scale has none of the three qualities as mentioned above.
- Ordinal Scale: The ordinal scale possesses the quality of magnitude. Here the numbers are assigned to the object to determine the relative extent to which certain characteristics are possessed, i.e. identifying whether an object has less or more characteristic than another object.
- Interval Scale: It is a scale in which the objects are rated in such a way that numerically equal distance on the scale depict the equal distance in the traits being measured. The interval scale possesses both the magnitude and equal intervals, but no absolute zero.
- Ratio Scale: It is the highest scale that allows the researcher to identify the objects, assign rank or order to the objects and compare the differences or intervals. This shows that ratio scale possesses all the three qualities, Viz. Magnitude, equal intervals and absolute zero.
Thus, these are the primary scales of measurement used by the researcher on the basis of the type of variable included under study.