| Abstract: | This study investigated the validity of the Poly-Detect procedure to determine the approximate simple dimensionality structure and to quantify the degree of multidimensionality present in polytomous data through simulation and real data analysis. Both unidimensional and two-dimensional data were generated in the simulation study for the complete and the BIB data. The simulation results showed that the dimensionality structures were similar between the corresponding complete data and the BIB data as identified by the Poly-Detect procedure. Also, the simulation results indicated that the number of response categories of items did not affect the performance of the Poly-Detect procedure in quantifying the degree of multidimensionality of polytomous data. Based on the simulation results, a subjective scale of the degree of multidimensionality of a data set was developed. Application of the Poly-Detect procedure on the 1992 NAEP eighth-grade reading data indicated that the degree of multidimensionality of the entire 1992 NAEP eighth-grade reading item pool was moderate at most. |
