The quantitative variable represents measurable quantities, and the values of these variables can be ordered in logical and natural ways (numeric data). For example,
- Size of shirts – 39,40,42, and so on.
- Per kilo prices of vegetables – Rs. 30, Rs. 35, Rs. 50, and so on.
- The number of colleges in a city – 5, 10, 15, and so on.
- Heights of children – 1.2 m, 1.23 m, 1.5 m, and so on.
Under the quantitative variables, we have two types of variables, one is called discrete variable, and the other is called a continuous variable.
Discrete Variable: These variables can take a finite number of values. For example, the number of children in a family – 0,1,2,3, etc. or number of branches of a school in a city – 0,1,2,3,4,5, and so on.
Continuous Variable: These variables can have an infinite number of values. For example, Lenght of a wire is 1.5 meters, 1.55 meters, 1.6 meters, and so on. So it can take an infinite range of numbers as a value.
On the other hand, the qualitative variable represents categories that include ordinal and nominal data. The values of these variables can’t be ordered logically and naturally (non-numeric data). For example,
- Names of cities – Kanpur, Mumbai, Kolkata, etc.
- Colors of hair – Black, White, Brown, etc.
- Performance – Good, Excellent, Bad, etc.
- Tastes of Food – Sweet, Salty, Neutral, etc.
Usually, numbers are assigned to qualitative variables. For example, Names of cities (X), x1 = 1 = Kanpur, x2 = 2 = Mumbai, and so on.
Nominal variable: A nominal variable, is one that has two or more categories, but it does not maintain any ordering to the categories. For example, a binary variable (such as yes/no question) is a categorical variable having two categories (yes or no) and there is no intrinsic ordering to the categories.
For example:
- Hair color is also a categorical variable having a number of categories (blonde, brown, brunette, red, etc.) and again, there is no agreed way to order these from highest to lowest.
A purely nominal variable is one that simply allows you to assign categories but you cannot clearly order the categories. If the variable has a clear ordering, then that variable would be an ordinal variable.
Ordinal variable: An ordinal variable is a variable that keeps the position of something in a list.
- Two judges give ranks to a fashion model.
- Two persons give ranks to food prepared or their scores are ranked.
These observations are the ranks of two variables (two judges). For example, 1st, 2nd, 3rd positions, etc.
Interval variable: An interval variable is similar to an ordinal variable, except that the intervals between the values of the numerical variable are equally spaced.
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