Ayoung girl decides that she wants to become an olympic swimmer. she takes swimming lessons, joins her school's swimming team, reads magazine articles about champion swimmers, and goes to swimming meets at a nearby college. this is an example of

answer; i believe the best and correct answer is stronger bonds between the nations of africa;

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.