PMC

Item characteristic (left) and item information (right) curves for the 11-item 2PL IRT model.

Test information and standard error of measurement for the 11-item 2PL IRT model.

The serial position effect in the current list learning data. The trendline represents the quadratic function that best fits the data. Error bars represent 95% confidence intervals.

Test information and standard error of measurement for the 15-item (left) and 13-item (right) 2PL IRT models. The similarity between the curves suggests that the measurement properties of the 15-item model are not impacted by the removal of the final two items.

Scree plot depicting the results of the modified parallel analysis for the 15-item list. The real data (solid line) show evidence of a two-factor solution based on the second eigenvalue >1.0 and the difference between the second eigenvalues of the real data the simulated data (dashed line).

Item characteristic (top row) and item information (bottom row) curves for the 15-item (left column) and 13-item (right column) 2PL IRT models. In the 15-item model, items 1, 12, 14, and 15 (broken lines) function dissimilarly from the remaining items (solid lines). Removing items 14 and 15 to yield a 13-item list did not improve the fit of items 1 and 12.