Variables can be classified as qualitative or quantitative. Consider the people of a city.

(i) If the people in the city are classified by their gender (male or female) or by their mother tongue or by religion, a person takes on values that are not numbers. Such a variable, here the people of the city, is said to be qualitative variable.

(ii) If the people in the city are classified by age, height or weight a person takes on values that are numbers. Such a variable, in this case the people of the city, is said to be quantitative variable.

In general a variable is said to be qualitative if it takes on values that are names or labels and a variable is quantitative if it takes on values that are numbers.