The difference between an experimental design and a quasi-experimental design is that __________.

A) only quasi-experimental designs use random assignment
B) quasi-experimental designs are specifically designed to investigate alcohol effects; experimental designs are not
C) only experimental designs use random assignment
D) experimental design studies are specifically designed to investigate alcohol effects; quasi-experimental designs are not

Experimental designs and quasi-experimental designs both use manipulation of an independent variable to observe its effect on a dependent variable, but experimental designs utilize random assignment of participants to groups while quasi-experimental designs do not. Therefore, option C is correct. Options B and D are incorrect because neither type of design is specifically designed to investigate alcohol effects. Option A is incorrect because random assignment is used in experimental designs but not necessarily in quasi-experimental designs.