D-Efficiency = 1 ?

Question

I use Alternative Specific design with 23 attributes. I have one main attribute and all the others depend on it. There is no other prohibitions across the attributes.
I have 2400 interviews 16 tasks and 3 alternatives in each. In what cases D-Efficiency may be only 1?

Answer 1

D-Efficiency is rather measure for relative strength of a design. So it will have value of 1 only if your design has the same efficiency as you reference one. Usually you will assume perfectly orthogonal and balanced design as a reference. Or other design suposed to be good enough. If you are testing for prohibitions, for example, you can choose design without them as your reference point.