Whenever we put a prohibition in a CBC design, it creates discord between 1-way and 2-way frequency counts. If we perfectly balance non-prohibited 2-way frequencies, it sacrifices balance in 1-way frequencies. Ask for perfect 1-way frequency and it disturbs 2-way frequencies. Sawtooth Software’s CBC designs have a fixed (and non-adjustable) way of trading off 1-way vs. 2-way balance when prohibitions are specified. Other designers deal with the situation according to their goals. The next generation Sawtooth Software CBC designer (for Discover) will allow users to tune the tradeoff between 1-way and 2-way frequencies. We raise the issues and see how the tradeoff between 1-way and 2-way frequencies affects the D-efficiency criterion and traditional MNL precision.
