Who should have the power to define abnormality? Societies (popular vote), political groups, governmental/legal agencies, or mental health professionals?

What might be the advantages and disadvantages to allowing one or all of these groups have the final say?

Governmental/legal agencies,

Explanation: Allowing a government or legal agency to have a say on abnormality will have huge advantages of making the populace see it as very vital the need to maintain normal process of doing things without violating set out laws and order. The disadvantage is that the agency might violate the laws which they have the power to speak against and no one will have the audacity to confront them with full force.

can you give more details

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.