To assess the impact of test difficulty on persistence of effort, researchers plan to give one group of children relatively easy tests and another group more difficult tests. to reduce the chance that the children in one group are more intelligent than those in the other group, the researchers should make use ofa)random assignment. b)the double-blind procedure. c)naturalistic observation. d)operational definitions.

A)random assignment.

Explanation:

Random assignment: In psychology, the random assignment is defined as the utilization of chance procedures in any of the psychological experiment to confirm that each subject that is being chosen in the study has got the equal opportunity to be assigned or selected in a particular group.

Every participant or the subjects are equally assigned to different groups (treatment group, experimental group) during an experiment, research, or study.

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