This chart shows American troop strength during what conflict

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.        

your answer is "graduates" hope this

the answer is d.index

answer; taking detailed notes during the interview;