Ascal(tm) 3.20: 2- and 3-parameter Irt Calibration Program

ASCAL analyzes data files (in ASCII format) of test item responses produced by optical mark readers (test scanners) or by manual data entry -- the same format used by ITEMAN, RASCAL, and XCALIBRE -- to compute item response theory (IRT) parameter estimates for a 2- or 3-parameter IRT model. It uses a Bayesian modal approach to estimation and also provides Pearson chi-square statistics of item fit.

The program distinguishes between items that have been omitted and items that have not been answered by an examinee. Using this information, it can give partial credit for omitted items in computations while excluding "not-reached" items from the computations. Items from different tests can also be linked onto a common scale in a single calibration run. It can also compute Bayesian modal (MAP) scores for examinees, which can be used in additional analyses by standard statistical programs.

ASCAL requires DOS 3.3 or higher, with 640KB RAM. A 486DX or math coprocessor is strongly recommended.