Measurement scales are classified popularly under four categories: Nominal, Ordinal, Interval and Ratio scales.
Ordinal Scale data share some properties of numbers of arithmetic but not all properties. For example, we can classify the cars as small, medium and big depending on the size. In the ordinal scales, the order of the values is important but the differences between each one are unknown. Look at the example below.
How did you feel after using fedora linux?
The answers would be:
(1) Very unhappy (2) Unhappy (3) Okay (4) Happy (5) Very happy
n each case, we know that number 5 is better than number 4 or number 3, but we don’t know how much better it is. For example, is the difference between “Okay” and “Unhappy” the same as the difference between “Very Happy” and “Happy?” In fact, we cannot say anything.
Similarly, a medical practitioner can say the condition of a patient in the hospital as good, fair, serious and critical and assign numbers 1 for good, 2 for fair, 3 for serious and 4 for critical. The level of seriousness can be from 1 to 4 leading to 1 < 2 or 2 < 3 or 3 < 4. However, the value here just indicates the level of seriousness of the patient only.