Maya is conducting an intervention to improve physicians' communication with patients. She has one group of physicians participate in a workshop on effective communication styles and the other group of physicians read a paper about immunizations. To measure effective communication, she then has judges code audiotapes of the physicians' interactions with patients. She finds that the communication workshop was effective in improving their communication, but mostly for young physicians - it was less effective for old physicians. In this study, the age of the physicians was a(n):
a. confound
b. mediator
c. moderator
d. artifact
e. third variable
Answer: c. moderator
Psychology