To Study the Effects of Noise on Worker Productivity,researchers Have

Multiple Choice

To study the effects of noise on worker productivity,researchers have one group of people work in a noisy room and a second group work in a quiet room.To be sure that any differences in the productivity of the two groups actually result from the different noise levels,the researchers should use

A) the case study.
B) correlational measurement.
C) naturalistic observation.
D) random assignment.