How Intervening Variables Work in Sociology

The growing disparity between income of those with college degree versus those without illustrates the way occupation acts as an intervening variable between education and income.
Impact of Educational Attainment on Income in 2014. Pew Research Center

An intervening variable is something that impacts the relationship between an independent and a dependent variable. Usually, the intervening variable is caused by the independent variable, and is itself a cause of the dependent variable.

For example, there is an observed positive correlation between level of education and level of income, such that people with higher levels of education tend to earn higher levels of income.

This observable trend, however, is not directly causal in nature. Occupation serves as the intervening variable between the two, since education level (the independent variable) influences what kind of occupation one will have (the dependent variable), and therefore how much money one will earn. In other words, more schooling tends to mean a higher status job, which in turn tends to bring a higher income.

How an Intervening Variable Works

When researchers conduct experiments or studies they are usually interested in understanding the relationship between two variables: an independent and a dependent variable. The independent variable is usually hypothesized to be the cause of the dependent variable, and the research is designed to prove whether or not this is true.

In many cases, like the link between education and income described above, a statistically significant relationship is observable, but it is not proven that the indirect variable is directly causing the dependent variable to behave as it does.

When this occurs researchers then hypothesize what other variables could be influencing the relationship, or how a variable might "intervene" between the two. With the example given above, occupation intervenes to mediate the connection between level of education and level of income. (Statisticians consider an intervening variable to be a kind of mediating variable.)

Thinking causally, the intervening variable follows the independent variable but precedes the dependent variable. From a research standpoint, it clarifies the nature of the relationship between the independent and dependent variables.

Other Examples of Intervening Variables in Sociology Research

Another example of an intervening variable that sociologists monitor is the effect of systemic racism on college completion rates. There is a documented relationship between race and college completion rates.

Research shows that among 25 to 29-year-old adults in the U.S., Asian Americans are most likely to have completed college, followed by whites, while Blacks and Hispanics have much lower rates of college completion. This represents a statistically significant relationship between race (independent variable) and level of education (dependent variable). However, it is not accurate to say that race itself influences level of education. Rather, the experience of racism is an intervening variable between the two.​

Many studies have shown that racism has a strong effect on the quality of K-12 education that one receives in the U.S. The nation's long history of segregation and housing patterns today mean that the nation's least-funded schools primarily serve students of color while the nation's best-funded schools primarily serve white students.

In this way, racism intervenes to affect the quality of education.

Additionally, studies have shown that implicit racial biases among educators lead to Black and Latino students receiving less encouragement and more discouragement in the classroom than white and Asian students, and also, that they are more regularly and harshly punished for acting out. This means that racism, as it manifests in the thoughts and actions of educators, once again intervenes to impact college completion rates on the basis of race. There are numerous other ways in which racism acts as an intervening variable between race and level of education.

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Crossman, Ashley. "How Intervening Variables Work in Sociology." ThoughtCo, Feb. 1, 2018, thoughtco.com/intervening-variable-3026367. Crossman, Ashley. (2018, February 1). How Intervening Variables Work in Sociology. Retrieved from https://www.thoughtco.com/intervening-variable-3026367 Crossman, Ashley. "How Intervening Variables Work in Sociology." ThoughtCo. https://www.thoughtco.com/intervening-variable-3026367 (accessed May 28, 2018).