The rates of both preterm and low-birth-weight births are decreasing in the United States

The addition of a control group

a. permits a basis for comparison when the independent variable is manipulated. b. increases the validity of the operational definition. c. works best with human participants. d. assures a random sample of subjects. e. is only necessary in correlational studies.

"I got an A on the last exam because I'm a good student" illustrates a/an

_________ attribution. (a) internal (b) external (c) illusory (d) none of the above