Which of the following would qualify as an event of 'domestic violence' within a state that would warrant the involvement of the national government? a. a massive political march b. a devastating tornado c. a crime spree d. an attack by a foreign power

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.