Figure 2.

The ratio of the variance of the intervention effect when using design matrices X ₁ (top) and X ₂ (bottom) relative to the optimal design (given in Figure 1) is shown for a range of possible combinations of $({\sigma }_c^2,{\sigma }_{\epsilon }^2)\in [0.001,0.25]\times [0.25,4]$ [Colour figure can be viewed at wileyonlinelibrary.com]