Development, psychometric properties and new validity evidences of the web-based computerized adaptive test of English eCat

This paper describes the process of constructing the eCat test and provides information on the effects its normal operation had on its psychometric properties. Results obtained from 3224 students revealed that the 225 item pool has adequate reliability and good convergent validity with respect to self-reported English proficiency. Simulations showed that ability estimations are essentially unbiased and that a stopping criterion of over 15 items is required to achieve a reasonable level of precision. From 7254 eCat administrations the test psychometric properties have been computed again and compared with those of the preoperational eCat. Additional validity evidences are also presented.