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levels of measurement

Understanding Levels of Measurement in Statistics: Nominal, Ordinal, Interval, and Ratio

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Have you ever asked why some statistical tests work for a particular type of data and not another? This concern relates to a measure of data.

Classification refers to a system for describing a variable’s level of measurement in terms of the type of data and operations available to the same. There are four levels of measurement: nominal, ordinal, interval, and ratio.

Knowing about a different level of measurement helps in selecting appropriate statistical tests for your data. It will be essential when presenting or analyzing the results of your statistical investigation.

This article will focus on a detailed discussion of the four types of measurements at every level. Examples of each level of measures will be provided as well as information on how to select relevant statistical tests depending on the level of measurement.

Types of Measures in Statistics.

Scales of measurement are defined as a method of specifying and describing statistical variables in terms of their levels. Data is defined as well as what types of operations can take place against this data. These are normally nominal, ordinal, interval, and ratio measurements. They move from very limited information, providing just the base statistics.

What Is the Importance Of Levels Of Measurement?

The importance of measuring levels is that it determines the kind of mathematical operations and statistics used on any dataset. It is essential to use the right scale of measurement for meaningful analysis and a correct interpretation. The improper use of the wrong level may result in reading the information incorrectly; it is simply impossible to develop effective outcomes.

The four levels of measurement are nominal, Ordinal, Interval and Ratio.

  1. Nominal Level of Measurement

Data at the nominal level of measurement are simply categorized or labelled into different groups/categories at the most primary level. The categorisation is not ordered, let alone hierarchal.


  • Nominal data might include qualities.
  • Nominal data do not allow any mathematical operation like additions and subtractions.
  • Categories in nominal data do not cross-cut in that an observation fits just one category.


  • Colors (e.g., red, blue, green)
  • e.g. male/female/non-binary.
  • e.g., single, married/divorced.

2. Ordinal Level of Measurement

At the ordinal level, data is put in different categories that have a logical rank or ordering but have intervals that are not of any significant measure.


  • However, the differences in the ranking order cannot be well quantified with ordinal data.
  • The fundamental ones include ranking and comparing operations.
  • There are no exact figures for the variations that exist between different categories.


  • e.g. high school diploma, bachelor’s degree, master’s degree.
  • e.g. Low-income, Middle-income, High-income.
  • e.g. satisfied, very satisfied, dissatisfied, dissatisfied, not satisfied at all.

3. Interval Level of Measurement

Data arranged at this level of measurement is put in orderly sequences of which intervals separating them are constant and measurable. Nonetheless, there exists no absolute nothingness.


  • Interval data, as opposed to ratio data, are amenable to such simple mathematical operations as addition and subtraction.
  • Without an absolute zero, interval data can not be used for meaningful rations or multiplication-division operations.


  • Temperature in Celsius or Fahrenheit
  • IQ scores
  • Years of calendar (e.g., 2023, 2024, 2025)

4. Ratio Level of Measurement

At the ratio level measurement, this is the highest precision of degree; here it has mean orders; it has constant intervals and an absolute zero point. This enables all algebraic operations.


  • Any mathematical operation such as multiplication and division can be carried out on ratio data.
  • Ratio values have meanings and mean something in terms of an absolute Zero point.


  • Age
  • Height
  • Weight
  • Income

Measurement level of a variable.

To conduct accurate data analysis, it is necessary to establish the degree of measurement of the variable. Consider the following guidelines:

  • Nominal Level: These variables are characterized by their categories that have no natural ordering. To verify that this level suits you, try whether it is possible to change the orders in the coding options without making sense; it is essential to compute the variations between the categories in any case.
  • Ordinal Level: The interval between categories in ordinal is not equal to intrinsic order. If you could rank them and distinguish one from another but not measure their differences precisely, then it is an ordinal variable.
  • Interval Level: Interval vari¬ables never reach absolute nothingness except for incre¬ments of the same magnitude as the category separations. Use the ability to do addition and subtraction on the data in order to test whether it has a degree of abstraction.
  • Ratio Level: Order, interval and absoluteness are characteristic of ratio variables. In order to establish what this level would be, consider whether or not you are able to do math involving multiplication and division, for instance, to the zero point has significance.

Choosing a Statistical Test for Various Measurements.

Your selection of a statistical test is largely determined by the nature of the measurement for your variables. Here are some general guidelines:

  • Nominal and Ordinal Data: For nominal and ordinal data, non-parametric tests such as the chi-square test, Mann-Whitney U test and Kruskal-Wallis test can be applied. Such tests do not imply the normality of data.
  • Interval and Ratio Data: Parametric tests are applicable when it comes to interval and ratio data; this is since they assume that the data has a normal distribution. These include t-test for comparing means, ANOVA for more than one group and regression for analyzing relations.


The Nominal to Ratio Scale Framework for Understanding Data in Statistics. To get valid statistical interpretations of what you choose to analyze, proper selection of variable levels or statistics becomes crucial. Researchers can thus reach valid opinions and decisions based on the particular traits of every level by knowing which statistical tests relate to which field ranging from health care to education and so forth. In essence, using the correct level of measurement is a critical value calculator in all statistics because it helps to make the right understanding of the information presented.

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