Describe some factors that contributed to american indian economies

Indians cultivated and developed many plants that are very important in the world today. Some of them are white and sweet potatoes, corn, beans, tobacco, chocolate, peanuts, cotton, rubber and gum. Plants were also used for dyes, medicines, soap, clothes, shelters and baskets.

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; /// i believe the correct answer is general act charters;