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Wikipedia: Intervening variable. Excerpt: An intervening variable is a hypothetical internal state that is used to explain relationships between observed variables, such as independent and dependent variables, in empirical research. An intervening variable facilitates a better understanding of the relationship between the independent and dependent variables when the variables appear to not have a definite connection. They are studied by means of operational definitions and have no existence apart. URL: en.wikipedia.org/wiki/Intervening_variable