How do you know a good decision?

During the humane assessment primer course, there were several excellent questions popping up. One of them was: How do you know a good decision?

In other words, how do you know when the facts in front of you are enough to make the decision. This concern is particularly relevant for managers.

My position goes as follows:

If you do not know what you need for making a decision, you are probably the wrong person to make it.