A variable is some attribute that describes something (ie. a person, place, thing, or idea). The value of this variable can "vary" between entities. For example a variable of a person could be their hair or eye colour, which can take different values for different peoples.

Classifications

Variables can be classified into a few different categories and sub categories depending on the forms they take.

Qualitative

Qualitative variables are any variables in which their values belong to a category, instead of a magnitude.

Examples:

• A persons blood type (A, B, AB, O)
• A persons hair Colour (Brown, Black, Blonde, etc.)
• An animals species (Dog, Cat, Bird, etc.)

Quantitative

Quantitative variables are any variables in which their values take on numerical values that represent different magnitudes of a variable.

Discrete

A quantitative variable is considered discrete if it's possible values form a set of separate numbers (ie. natural numbers or integers)

Examples:

• The number of siblings a person has (ie, 2, 3, etc.)
• The number of people in the world (ie, 7 billion, 3,000, etc.)

Continuous

A quantitative variable is considered continuous if it's possible values form an interval (ie. the reals between 3 and 4).

Examples:

• The temperature in a room (e.g., 20.5 °C)
• The weight of a person in kg's (eg. 20.1 kg)