@conference {1238, title = {Relative precision of ability estimation in polytomous CAT: A comparison under the generalized partial credit model and graded response model}, booktitle = {Paper presented at the annual meeting of the American Educational Research Association}, year = {2002}, note = {$\#$WA02-01 {PDF file, 735 KB}}, address = {New Orleans LA}, author = {Wang, S and Wang, T.} }