Who chooses the leader in a parliamentary system

In a parliamentary system, the leader is a member of the parliament chosen by the parliament.

Unlike other systems where the people choose both their legislators and their chief executive, in a Parliamentary system the people only choose their legislators and the legislators choose the leader.

the leader is chosen by parliament

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.