Interval Variable – Definition, Types, Examples

Interval Variable

Interval Variable

An interval variable is a quantitative variable for which the difference between two values is meaningful and measurable. Interval variables are often used in scientific research. One example of an interval variable is temperature, because the difference between two temperatures (e.g., 40 degrees Fahrenheit and41 degrees Fahrenheit) is meaningful and can be measured.

Interval variables are different from ordinal variables, which also have meaningful differences between values but cannot be meaningfully measured. For example, while the difference between “somewhat satisfied” and “very satisfied” on a survey may be meaningful, it is not something that can be easily measured.

Interval Variable In Research

An interval variable is often used in research to measure things like temperature, time, or weight. Interval variables are important because they allow researchers to compare data points that are not directly next to each other on the scale. For example, if two data points are both 10 units apart on an interval scale, we can say that they are equally distant from each other. However, if one data point is 10 units away from the zero point and the other is 20 units away, we can say that the second data point is twice as far away from the zero point as the first data point.

Types of Interval Variable

There are four types of interval variables:

  • Equal-interval
  • Rank-order
  • Deviation
  • Ratio


Equal-interval interval variables are those that have an equal distance between each value on the scale. An example of an equal-interval interval variable is temperature measured in degrees Fahrenheit or Celsius. The value of 50 degrees is exactly twice as much as 25 degrees and 10 times as much as 5 degrees.


Rank-order interval variables are those in which the order of the values is meaningful, but the specific values themselves are not. An example of a rank-order interval variable is social class. In many societies, there are five social classes: upper class, upper middle class, lower middle class, working class, and poor.


Deviation interval variables measure the deviation of a value from a reference point. The deviation is the distance from the value to the reference point. An example of a deviation-interval variable is height of children. The height of each child would be compared with an average for the population.


A ratio interval variable is a type of measurement that is used to quantify the relationship between two or more values. This type of variable is often used in research to compare and contrast data sets.

Example of Interval Variable

An Example of Interval Variable could be: To measure how much people like different flavors of ice cream. You could give each flavor a score from 1 to 10, and then compare the scores to see which flavor is most popular.

Interval variables are also used in statistics and data analysis. For example, you might use an interval variable to track the average temperature over time.

When to use Interval Variable

They are often used in scientific research to measure things like temperature, weight, height, or length. Interval variables are different from categorical variables, which can only be counted or classified, but not measured on a scale. When choosing whether to use an interval or categorical variable, it is important to consider what type of data you are working with and what type of analysis you plan to do.

If you want to compare two groups on an interval variable, you will need to use a t-test or ANOVA. These tests assume that the data is normally distributed, so if your data is not normal, you may need to transform it before running the test. You can also use regression to predict an interval variable based on other variables in your data set.

Purpose of Interval Variable

The purpose of an interval variable is to allow researchers to measure the distance between two data points. Interval variables can be used to measure both continuous and discrete data.

Advantages of Interval Variable

There are some advantages to using interval variables in research:

  • They allow for more precise measurements than other types of variables.
  • Interval variables are less affected by outliers than other types of variables.
  • They can be used to calculate a variety of statistics, including means, standard deviations, and correlations.

Limitations of Interval Variable

Some Limitations of Interval Variable are:

  • Interval variables can only be used with data that is measured on an interval scale.
  • Because interval variables have equal intervals, they cannot be used to measure ratios.
  • These Variables are affected by outliers, or extreme values that are not representative of the rest of the data.

About the author

Muhammad Hassan

I am Muhammad Hassan, a Researcher, Academic Writer, Web Developer, and Android App Developer. I have worked in various industries and have gained a wealth of knowledge and experience. In my spare time, I enjoy writing blog posts and articles on a variety of Academic topics. I also like to stay up-to-date with the latest trends in the IT industry to share my knowledge with others through my writing.