Nominal Variable

A nominal variable is a type of categorical variable that can have two or more categories. However, there is no ordering within these categories. A nominal variable does not have any numerical characteristics and is qualitative in nature. If a variable has a proper numerical ordering then it is known as an ordinal variable.

A nominal variable can be coded but arithmetic operations cannot be performed on them. In other words, nominal variables cannot be quantified. In this article, we will learn more about a nominal variable, a nominal scale and several associated examples.

A nominal variable along with a dichotomous and an ordinal variable form the three types of categorical variables. A dichotomous variable is a subtype of a nominal variable that can have only two levels or categories. An ordinal variable on the other hand can have two or more categories, however, these can be ranked or ordered. Apart from categorical variables, other types of variables such as interval and ratio variables are also used.

Nominal Variable Definition

A nominal variable can be defined as a categorical variable in which the categories cannot be ordered. A nominal variable might be numeric in nature but it cannot have any numerical properties. This type of variable is assigned to nominal data as such type of data is non-numerical.

Nominal Variable Examples

An example of a nominal variable is hair color. This is because hair can be of different colors such as blonde, black, brown, red, etc. These categories cannot be ordered and neither can any operations be performed.

An example of a nominal variable is a person being asked if she owns a Macbook. The answer can either be yes or no. Thus, Macbook ownership can be categorized as either yes or no.

A nominal scale is a level of measurement where only qualitative variables are used. On such a scale, only tags or labels can classify objects. There are three other scales that are used for measurement levels - ordinal, interval, and ratio. A nominal variable is part of a nominal scale. In case a number is assigned to an object on a nominal scale there is a strict one-to-one correlation between the object and the corresponding numerical value. Thus, the variables in such a scale have no numeric property.

Nominal Scale Examples

An example of a nominal scale is categorizing dogs on the basis of their breeds (E.g. German shepherd, Husky, Samoyed, etc.).

Another example of a nominal scale is putting cities into states. (E.g. Seattle is in Washington).

The two main important characteristics of nominal variables are given as follows:

• Even though a nominal variable can take on numeric values, however, they cannot be quantified. In other words, arithmetic and logical operations cannot be performed on a nominal variable.
• The categories under nominal variables cannot be assigned a rank thereby, they cannot be ordered. Thus, a nominal variable is qualitative in nature.

A nominal variable can be classified either based on the collection technique or based on the numeric property. The nominal variable types are given as follows:

• Open-Ended Nominal Variable - When participants are asked open-ended questions such that they are free to respond in any way they like it is known as a nominal variable. For example, "How can a teacher improve his teaching methods?" is an open-ended nominal variable. Information collected using this variable is usually very detailed.
• Closed-Ended Nominal Variable - When the response of participants to a question has been restricted then such a question forms a closed-ended nominal variable. "How can a teacher improve his teaching methods? a) Acquiring better knowledge, b) Improving communication, c) Demonstrating flexibility. This is an example of a close-ended approach.
• Numeric and Non-Numeric Nominal Variable - A numeric nominal variable can take on a quantitative value but does not have any numeric property. For example, phone numbers. A non-numeric nominal variable neither takes on a numerical value nor does it have any numeric property. For example, an open-ended / closed-ended question.

A nominal and an ordinal variable are types of categorical variables. Both variables are qualitative in nature. The table given below highlights the main differences between nominal and ordinal variables.

Related Articles:

• Data Handling
• Data
• Data Collection
• Categorical Data

Important Notes on Nominal Variable

• A nominal variable is a categorical variable that does not have any intrinsic ordering or ranking.
• Such a variable is qualitative in nature and arithmetic or logical operations cannot be performed on it.
• A nominal variable follows a nominal scale of measurement.
• The types of nominal variables are open-ended, closed-ended, numeric, and non-numeric variables.

What is a Nominal Variable?

A variable consisting of categories that cannot be ranked or ordered is known as a nominal variable. A nominal variable cannot be quantitative.

Is a Nominal Variable a Type of Categorical Variable?

Yes, a nominal variable is a type of categorical variable. Other types of categorical variables are ordinal variables and dichotomous variables.

Is a Nominal Variable Qualitative in Nature?

Yes, a nominal variable is qualitative in nature. This means that arithmetic operations and logical operations cannot be performed on a nominal variable.

What Measurement Level is Followed by a Nominal Variable?

A nominal scale is the level of measurement used by a nominal variable. Such a scale is qualitative in nature and uses labels and tags to categorize data.

What is the Difference Between an Open-Ended and Closed-Ended Nominal Variable?

An open-ended nominal variable lets the participant respond freely while a closed-ended nominal variable is usually in the form of multiple-choice questions and restricts the participant's views.

Can a Nominal Variable Be Numeric?

Yes, a nominal variable can be in the form of a number however, it will not have any quantitative property. Thus, arithmetic operations cannot be performed on such a variable.

What is the Difference Between an Ordinal and a Nominal Variable?

In an ordinal variable the categories can be ranked and ordered however, in a nominal variable no ranking is possible.