8.5 Item-level Relative Fit measures (Cont’d)

If this item is a DINA item, we have $$P\left(10\right)=P\left(01\right)=P\left(11\right)$$ This is equivalent to say $$\left[\begin{array}{cccc}0& 1& -1& 0\\ 0& 0& 1& -1\end{array}\right]\left[\begin{array}{c}P\left(00\right)\\ P\left(10\right)\\ P\left(01\right)\\ P\left(11\right)\end{array}\right]=\left[\begin{array}{c}0\\ 0\end{array}\right]$$ Or, $$RP=0$$