Efficiency is staying busy with no idle moments.
Effective is getting the maxim results with the minimum effort.
A young 2nd Lieutenant was ordered to climb a mountain in Vietnam by way of a valley. It was dense jungle to the new position. He had two men in front with machete's chopping away the undergrowth, two behind resting and two behind them sharpening more machetes. The rest of his unit was taking turns moving forward doing all these jobs. So efficient. His commander radioed to see how he was doing. Of course the answer fantastic. Later the commander was checking on the operation from a helicopter radioed him again. "Your going up the wrong valley." Not very Effective. True story. We make sure what we teach works. Not just busy activity.