In a research setting one variable has been different for the experimental group than it has been for the control group. What kind of variable is this?

A scientific theory can be thought of as a(n) ________

a. personal opinion b. established truth c. system of assumptions d. empirical proof

In the United States, substance use is ______ before adolescence, ________ by the end of secondary school

a. common; but very prevalent b. often restricted to caffeine; butmost had used alcohol daily c. rare; but fairly common d. unheard of; and rare