A stranger approached a museum curator and offered him an ancient bronze coin. The coin had an authentic appearance and was marked with the date 544 bce. The curator had happily made acquisitions from suspicious sources before, but this time he promptly called the police and had the stranger arrested. Why

The curator realized that the coin is dated 544 bce. It would be impossible for a coin maker to date a coin as "created before Christ" if that coin maker did not know who Christ would be, nor when he would be born, nor that his birth would be used for dates.

Explanation:

A coin maker who lived before Christ and created coins before Christ was born, could not create a coin dated 544 bce. In short, this coin maker did not know that Christ would be born, nor that he would be relevant. Furthermore, the coin maker did not know the date that Christ would be born, so he could count the years and know exactly the date the coin was being created. For this reason, the currency shown in the question above can only be counterfeit.

explanation:

with the profits from the european sales, merchants purchased europe's manufactured  goods, including tools and weapons. then the merchants shipped those manufactured  goods, along with the  american  sugar and rum, to west africa where they were bartered for  slaves.

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.