Just Sociology

Understanding the Three Types of Variables in Statistics

In the field of statistics, variables play a crucial role in analyzing data and drawing conclusions from it. Variables refer to the characteristics or attributes that can vary in a population or a sample.

They are broadly classified into three categories: interval/ratio, ordinal, and nominal/categorical variables. Each of these categories has its own unique characteristics and can be measured using different statistical techniques.

This article aims to discuss these three types of variables and provide a questionnaire example to clarify their differences.

Types of Variables

Interval/ Ratio Variables

Interval/ratio variables are measured on a scale that has identical distances between adjacent points. In other words, the intervals between values on the scale are equal.

Examples of interval/ratio variables include age and time. They have a fixed zero point, meaning that zero represents the absence of the variable being measured.

Interval/ratio variables are amenable to a wide range of statistical analyses, including mean, standard deviation, and regression.

Ordinal Variables

Ordinal variables are rank-ordered based on their magnitudes, but the distances between adjacent values are not equal. For example, suppose we asked a group of students to rate their academic performance on a scale of 1 to 5.

In that case, it is not necessary that the distance between 1 and 2 would be the same as between 4 and 5. Ordinal variables are often converted into numerical scores to facilitate analysis.

This is known as grouping interval variables. An example of an ordinal variable is socioeconomic status.

Nominal or Categorical Variables

Nominal or categorical variables consist of categories that cannot be ranked or compared in terms of their magnitudes. They are generally used to represent subjective responses or dichotomous variables such as male/female or “yes” and “no” questions.

Nominal or categorical data is analyzed using statistical techniques such as chi-square or contingency tables. Examples of categorical variables include occupation and city of residence.

Questionnaire Example

Real Number Questions

A common type of question in a survey is a real number question, such as age or hours studying per week. Real number questions are examples of interval variables as they are measured on a scale that has identical distances between adjacent points.

In other words, the differences between ages of 20 and 30 and 40 and 50 are equal because the scale uses the same units, years in this case. The mean, standard deviation or regression, is appropriate for analyzing the results of such questions.

Dichotomous Questions

Dichotomous questions are designed to produce a “yes” or “no” response, and thus they are a common feature of many surveys. For instance, a survey may ask if the participant is male or female.

Dichotomous questions are examples of nominal or categorical variables. They are amenable to statistical analysis using methods such as proportions, frequency tables, or contingency tables.

The analysis of dichotomous variables provides information on the proportion or percentage of the respondents who answered in the affirmative.

Rank-Ordered Categorical Questions

Rank-ordered categorical questions ask respondents to rank their responses according to their preferences. For example, participants may be asked how often they take a particular medication, and the options provided would be once a day, once a week, and once a month.

Such questions are often used to assess opinion, attitudes or preferences, and are examples of ordinal variables. They are analyzed using methods such as percentages or frequency tables.


Rank-Ordered Categorical Questions

Non-rank-ordered categorical questions ask respondents to categorize themselves into one of several categories. An example of such a question might be whether the participants general interest aligns with their career goals.

Such questions are examples of nominal or categorical variables. Statistical methods such as cross-tabulation or chi-square analysis are used to analyze them.


In conclusion, the type of variable used in a study is an essential factor that affects the statistical analysis methods chosen to answer the research question. There are three different types of variables: interval/ratio, ordinal, and nominal/categorical variables.

Understanding the fundamental differences between them allows researchers to choose the correct statistical methods to analyze their data. The questionnaire example provided helps to illustrate this distinction in the context of different question types.

In conclusion, understanding the different types of variables and their unique characteristics is crucial in the field of statistics, as it enables researchers to choose the correct statistical techniques to analyze their data accurately. By recognizing the significance of these variables, researchers can make informed decisions and draw valid conclusions from their studies.

Through the questionnaire example provided above, we hope to have clarified the differences between real number, dichotomous, rank-ordered, and non-rank-ordered categorical questions, which allows for more comprehensive and meaningful data analysis. Here are some frequently asked questions that may arise while learning about variables:



What is the difference between an interval and a ratio variable? An interval variable has identical distances between adjacent data points on its scale, while a ratio variable includes a fixed zero point.

2. How do you analyze ordinal variable data?

Ordinal variable data can be analyzed using grouping interval variables or by converting them to numerical scores. 3.

Can nominal or categorical data be ranked? No, nominal or categorical data cannot be ranked, as they lack any inherent order based on their magnitudes.

4. What statistical techniques are used to analyze nominal or categorical data?

Chi-square or contingency tables are widely used for analyzing nominal or categorical data. 5.

Are dichotomous questions analyzed differently than real number questions? Yes, dichotomous questions are an example of nominal or categorical data, while real number questions are examples of interval variables, meaning that they are analyzed using different statistical techniques.

Popular Posts