# Scale Variable: Definition

## What is a Scale Variable?

Scale variable doesn’t have an “official” definition; it’s one of those terms that has a slightly different meaning depending on where you’re using it. In a very general sense, the term is synonymous with measurement variable, although care should be taken to make sure this use is precise enough for whatever context you’re working in. For the behavioral sciences, trade and finance, and in SPSS, you’ll want to follow the more tailored definitions below.

Sometimes you might see texts from a variety of fields refer to “interval scale variable” or “nominal scale variable.” These are just variables that are on those particular scales (e.g. a variable on the interval scale or a variable on the nominal scale).

## SPSS

SPSS uses three different measurement levels.

SPSS measurement levels are limited to nominal (i.e. categorical), ordinal (i.e. ordered like 1st, 2nd, 3rd…), or scale. Essentially, a scale variable is a measurement variable — a variable that has a numeric value. Variables with numeric responses are assigned the scale variable label by default. This could be an issue if you’ve assigned numbers to represent categories, so you should define each variable within the measurement area individually.

## Behavioral Sciences

In behavioral science, a scale variable is defined in a different way. Specifically, they are defined in relation to a multivariate (multiple-variable) frequency distribution called a scale. For a population of objects (things that psychologists want to study, like intelligence, or depression), a scale exists if it’s possible to derive a numeric variable from the distribution that characterizes the objects (Maranell, 2017).

A variable from this type of distribution is called a scale variable. Scale scores (or, more simply, a score) are a result of these distributions. For example, an IQ score or a score on a depression scale are both derived from the above definition.

In trade and finance, a scale variable (S) is a measurement index, usually defined specifically within a particular context. For example:

• Kenen (2008) defines S as an index “the size of the decision making unit’s portfolio.” For example, S could be net worth for a household.
• Frischtak et. al (1994) defines S as “the average gross production within the class of largest plants of each industry expressed as a percentage of total industry gross production.”

## References

Frischtak et. al (1994). Market Structure and Industrial Performance, Volume 15. Taylor and Francis.
Kenen, P. (2008). International Trade and Finance: Frontiers for Research. Cambridge University Press.
Kent State University. SPSS Tutorials: Defining Variables. Retrieved October 27, 2017 from:https://libguides.library.kent.edu/SPSS/DefineVariables
Maranell, G. (2017). Scaling: A Sourcebook for Behavioral Scientists. Routledge.

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