Q-Matrix

• A $J\times K$ matrix of zeros and ones. $q_{jk}$ indicates whether skill $k$ is required to correctly answer item $j$.
• $X_{ij}$ be the response of examinee $i$ to item $j$, ${\alpha }_i=\{{\alpha }_{ik}\}$ be the binary skill vector.
• A cognitive design matrix that explicitly identifies the cognitive specification for each item.