Jessica has 9 kess dollars than daniel. altogether, jessica and daniel have 31 dollars. how much money does jessica have?

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.        

answer; broad features of society;