What government structure did the Aztec and the Inca have in common? A.
They allowed everyone to vote.
B.
They were ruled by emperors.
C.
They chose a priest to lead.
D.
They had a two-party system.

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.