Researchers were interested in whether relaxation training works better than fitness training in decreasing the number of headaches a person experiences. They randomly assigned 20 participants either to the fitness training group or a relaxation training group and then recorded the change in number of headaches for each group from pre-training to post-training. The independent variable in this study is ___.

The independent variable should be the 20 participants.

Explanation:

The dependent variable is what is being tested or changed and in this case it is what is being tested which is the headaches. The independent variable in what is being controlled and that would be the people.

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.        

it depends on which society you are referring to. many civilization performed rituals so the gods would with their growing season but the most well known is that of the aztecs. they would make sacrifices, usually animals, but sometimes humans as well.