Managerial decision making is the ability of individuals to develop a managerial approach to developing solutions.  Primarily because many situations will require you, as a manager, to come to quick and efficient solutions.  This may or may not be something that you can effectively do depending on a situation.   At the end, it is your responsibility to be effective time and time again.  Many people find this difficult because it can mean that you are developed continually as a leader.  make sure you are able to do so if and when you take that management role.