To Assess the Impact of Test Difficulty on Persistence of Effort,researchers

Multiple Choice

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 of

A) random assignment.
B) the double-blind procedure.
C) naturalistic observation.
D) operational definitions.