You may come across a variety of methods to assess a variable during a study. This article will describe the four primary kinds of measurement scales and provide some examples of them.
A nominal scale assigns a name or label to a category. These variables are categories that tell what something is, like different kinds of shoes (Sneakers, High Heels, Boots). More commonly in the types of studies you may read, you might have participants who identify themselves as “Hispanic” or “non-Hispanic.” They are the most basic form of measurement and don’t have any order to them. Sneakers are not “more than” boots.
Ordinal variables are similar to nominal variables, but they can have ordered categories, like different levels of education (High School Diploma, Associate’s Degree, Bachelor’s Degree). Another well-known ordinal variable is rank order, like a gold, silver, or bronze medal given out following an Olympic marathon. The scale just tells us the order in which the people are sorted. There is nothing about the distance or time between each of them.
An interval scale is a type of measurement scale that has equal distances between the points on the scale. This means that you can measure the difference between two points on the scale, but you can’t measure the absolute value of a point on the scale.
An example of an interval scale would be temperature, where you can measure the difference between two temperatures, but you can’t say that one temperature is twice as hot as another.
A ratio scale has the properties of an interval and nominal scale. It tells you the interval and nominal values and it also has a magnitude to give meaning to the nominal value. This is done by having a “true” zero.
An example of a ratio scale is weight, where there are nominal values like “heavy” and “light,” but there’s also a magnitude between them in terms of kilograms or pounds. Time is another ratio scale. We can say that a specific chemical reaction took twice as long as another.
The quick summary
The nominal scale is the most basic form of measurement. It does not have any ordered categories, it just tells you what something is like different kinds of shoes (Sneakers, High Heels, Boots). The ordinal scale has ordered categories but it’s only about order and there’s no distance or time between each category. An interval scale can measure distances between points on a measured variable but cannot provide absolute values for those points. A ratio scale has nominal variables with an “absolute” zero that lets us know how much difference there is in magnitude to nominal values like weight or time.
Let us know in the comments the types of measurement scales you find when looking at articles!