USS Tantalus (ARL-27) USS Tantalus (ARL-27) USS "Tantalus" (ARL-27) was one of 39 "Achelous"-class landing craft repair ships built for the United States Navy during World War II. Named for Tantalus (a legendary king of Lydia condemned to stand in a pool of water up to his chin and beneath fruit-laden boughs only to have the water or fruit recede at each attempt to drink or eat), she was the only U.S. Naval vessel to bear the name. Originally laid down as "LST-1117" on 10 October 1944 at Seneca, Illinois by the Chicago Bridge and Iron Company; launched on 2 January 1945; sponsored
Item response theory with higher math ability are more likely to get a math item correct. The exact value of the probability depends, in addition to ability, on a set of "item parameters" for the IRF. For example, in the three parameter logistic model (3PL), the probability of a correct response to a dichotomous item "i", usually a multiple-choice question, is: where formula_1 indicates that the person abilities are modeled as a sample from a normal distribution for the purpose of estimating the item parameters. After the item parameters have been estimated, the abilities of individual person are estimated for reporting purposes. formula_4,