Arab Educational Information Network

The study aimed at studying the effect of Percent of items in Anchor test on the accuracy of vertical equating using Rasch model for Mathematical Test. Three models of a two-level test in the Geometry subject were developed for fifth and sixth grades, each level consisted of (20), The first model included (3) common items, the second model included (6) common items, the third model included (9) common items between the two levels. The sample of the study consisted of (1031) students and the validity and reliability of the test were verified and the obtained results showed acceptable validity and reliability. The vertical equating was used by anchor test randomize groups using Rasch Model and Cross-validation and standard error were also used. The results showed that the accuracy of vertical equating increases by the increase of the anchor test items as the best obtained percentage was )45%( from the Items of Anchor Test. (Published abstract)