to nperson.</p></li>
<li><p>item: A pseudo item ID from 1 to nitem.</p></li>
<li><p>theta: Ability (i.e., theta) values used for generating responses.</p></li>
<li><p>difficulty: Item difficulty (i.e., b parameter) values used for generating responses.</p></li>
<li><p>group: Person groups (either 0 or 1).</p></li>
<li><p>group.effect: The magnitude of person group effect used for generating responses.</p></li>
<li><p>itemtype: Item groups (either 0 or 1).</p></li>
<li><p>itemtype.effect: The magnitude of it