Studies of biological factors affecting development of substance-use disorders implicate the neurotransmitter ____

In a matrix for a factorial design, the row means and column means represent the effects of:

a. extraneous factors. b. individual differences. c. an interaction. d. a single factor (variable).

According to the principle of conservation of energy, ____.

a. energy should never be expended unnecessarily b. energy is perceived differently by the different senses c. energy does not exist unless it is perceived by a living organism d. energy is never created or lost in a system, but is only transformed from one form to another