The purposeo f the presents tudy is to preparea pool of vocabularyi temsw hichc an be used for measuringb road range of ability and construct a scale for word meaningc omprehension. After preliminary testing and item analysis, 11 forms of vocabulary tests appropriate to first grade through graduate school have been built and administered. Applying the latent trait model, item characteristic parameters were estimated in each test. Making use of the common items contained in each set of adjucent level tests, scale values of latent trait in differentt ests were equated. Thus, difficultya nd discriminatingp ower of all items in 11 tests werec harcterizedo n the commons cale. Scoreso f subjectsw ere estimatedb y the maximuml ikelihoodm ethod. Precisiono f estimateso f each test is evaluated,a t all levels of ability, in terms of informationf unction
A stratified adaptive test of verbal ability has been built by use of this item pool. Administrationos f the test and an additionalq uestionaireo n the test indicatet hat the test is appropriate for from 6th graders through graduate students. An ability score of each subject was estimatedb y the maximuml ikelihoodm ethod. An informationc urvef or the set of items respondedb y each subjects hows that appropriatei temsa re selectedf or the subject. Amounto f informationi s peakeda t the neighborhoodo f the estimatedl evelo f the students' ability. All these results demonstrate that this stratified adaptive test can be used, practically, f or measuringb road range of verbal ability.