An intervening variable is a hypothetical variable used to explain causal links between other variables. Intervening variables cannot be observed in an experiment (that's why they are hypothetical). For example, there is an association between being poor and having a shorter life span.

What are intervening variables?

intervening variable (mediating variable)

A factor mediating the relationship between two other factors (see alsodependent and independent variables). Such a variable is causally situated between them and accounts at least partly for their association.

What are uses of intervening variable in research?

An intervening variable, sometimes called a mediator variable, is a theoretical variable the researcher uses to explain a cause or connection between other study variables—usually dependent and independent ones. They are associations instead of observations.