Effectiveness is doing things right to reach a desired outcome. Efficiency is doing things right with minimum effort.
Effectiveness is the answer to the question, “Which actions contribute to a defined goal or desired result?” The greater the contribution of the action, the greater its effectiveness.
Efficiency plays a role once it has become clear what action is to be taken. It is the answer to the question, “Is this the right action in terms of effort, time, energy or resources?” If this is the case, efficiency gains can still be achieved.