To study the effects of noise on worker productivity, researchers have one group of subjects work in a noisy room and a second group work in a quiet room. To ensure that any differences in the productivity of the two groups actually result from the different noise levels to which the groups are exposed, the researchers would use
a. the case study.
b. correlational measurement.
c. naturalistic observation.
d. replication.
e. random assignment.

Random assignment: In an experimental research, the term random assignment is defined as the phenomenon in which an experimenter uses the chance procedures while conducting the experiment or the research and therefore the researcher or the experimenter makes sure that every participant or subject who is the part of the research gets equal opportunity of getting selected in any of the group.

In the question above, the given statement signifies the random assignment.