How are efficiency and effectiveness related?

Ideally, we accomplish tasks efficiently and effectively, and they work hand in hand to achieve the very best results. However, it is possible to be efficient and ineffective, or, conversely, to be effective and inefficient. A Venn diagram would show two overlapping circles, with efficiency and effectiveness in the overlap and with each also occupying its own space as well.  Let's look at how this works.

Being efficient means using one's resources, labor, materials, information, and capital in such a way that the maximum results are achieved with the least amount in resources.  So, for example, if I am building a house, I will schedule my contractors and deliveries in such a way that I do not spend any money on materials until I need them and no contractors are scheduled until certain stages have been achieved. I will not have bricks and bricklayers sitting around doing nothing while the foundation is being dug. I will use information about the weather to not schedule driveway paving on a rainy day. This is efficiency, since I have taken care to not squander any of my resources.  However, I can do all of this and still have a house that no one wants to buy because the floors slant, the walls are out of square, and the basement floods.  Thus, I will have acted efficiently but ineffectively.

I can act effectively by building a house of good quality, one that meets our expectations of good housing, by focusing on the quality of my materials and the skills of my contractors.  To be effective means to accomplish what one intended to accomplish, and assuming one wants to accomplish the building of a marketable house, I can do so effectively.  However, I might very well take twice as long to build the house, for example, if I pay my contractors by the hour, as opposed to paying them by the job, or if I do not arrange deliveries efficiently, so that workers are tripping over materials they do not yet need, and I have spent money I did not need to spend yet.

Thus, it is possible to be efficient and not effective or effective and not efficient.  A good manager will try to the best of his or her ability to achieve both, although often we see a bit of a sacrifice in one or the other.  They should work hand in hand, but sometimes, they do not.