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The local item independence assumption underlying traditional item response theory (IRT) models is often not met for tests composed of testlets. There are 3 major approaches to addressing this issue: (a) ignore the violation and use a dichotomous IRT model (e.g., the 2-parameter logistic [2PL] model), (b) combine the interdependent items to form a polytomous item and apply a polytomous IRT model (e.g., the graded response model [GRM]), and (c) apply a model that explicitly takes into account the dependence at the item level (e.g., the testlet response theory [TRT] model). In this study, a simulation was conducted to compare the performance of these 3 approaches on number-correct score equating when degrees of testlet effect were manipulated. The traditional equipercentile method was used as an evaluation baseline. The results show that the 2PL and the TRT approaches produce comparable results that more closely agree with the results of the equipercentile method than the GRM does. And the number-correct equating using the 2PL is robust to the violation of local item independence.

1Boy Crusoe

By Allan Eric

Also published as" A Yankee Crusoe" . A 15 year old hard working and studious farm boy finds the lure of adventure on the seas as a merchant seaman more than he can resist. This is his story. " I was born in a little town in the State of Maine, near the close of the Civil War. My boyhood life did not differ materially from that of the average farmer's son in the remote country districts of New England--except, perhaps, that I read more and thought more. Hard work on the rugged soil, two terms each year in the little yellow country schoolhouse, a day's fishing now and then filled the early years of my life full to over-flowing. " What he gets is enough excitement and adventure to overflow his wildest dreams. How he experiences disaster and uses his wits and knowledge to overcome every problem makes for a great read. - Summary by Phil Chenevert