Under the two-parameter model (i.e., mdl groupinv(2, -2, 1, -1, 2)

Under the two-parameter model (i.e., mdl <- 2), set the following ability bounds:

Group 1—The lower bound is 2, and the upper bound is C1.

Group 2—The lower bound is 1, and the upper bound is C2.

Generate the five display graphs (e.g., Figs. 3.3, 3.4, 3.5, 3.6 and 3.7) sequentially in the graphics window for this example. In case the function groupinv is employed that will yield only a graph that is similar in appearance to Fig. 3.7, the following command line can be used:
> groupinv(2, -2, 1, -1, 2)