01906nas a2200133   4500008003900000245013200039210006900171300001200240490000700252520142100259100001801680700002101698856005301719       2012                          d00aComparison of Exposure Controls, Item Pool Characteristics, and Population Distributions for CAT Using the Partial Credit Model0 aComparison of Exposure Controls Item Pool Characteristics and Po  a159-1750 v723 a<p>
	This study investigated item exposure control procedures under various combinations of item pool characteristics and ability distributions in computerized adaptive testing based on the partial credit model. Three variables were manipulated: item pool characteristics (120 items for each of easy, medium, and hard item pools), two ability distributions (normally distributed and negatively skewed data), and three exposure control procedures (randomesque procedure, progressive&ndash;restricted procedure, and maximum information procedure). A number of measurement precision indexes such as descriptive statistics, correlations between known and estimated ability levels, bias, root mean squared error, and average absolute difference, exposure rates, item usage, and item overlap were computed to assess the impact of matched or nonmatched item pool and ability distributions on the accuracy of ability estimation and the performance of exposure control procedures. As expected, the medium item pool produced better precision of measurement than both the easy and hard item pools. The progressive&ndash;restricted procedure performed better in terms of maximum exposure rates, item average overlap, and pool utilization than both the randomesque procedure and the maximum information procedure. The easy item pool with the negatively skewed data as a mismatched condition produced the worst performance.</p>
1 aLee, HwaYoung1 aDodd, Barbara, G  uhttp://epm.sagepub.com/content/72/1/159.abstract