Estimation of Item and Ability Parameters

The estimation of ability parameters when item parameters are known was considered in chapter 5 (see also, Swaminathan, 1983). While the problem of estimating ability parameters when item parameters are given is reasonably straightforward, the simultaneous estimation of ability and item parameters raises several problems. The estimators in such situations may not possess desirable properties. Despite some of the problems that exist, several estimation procedures are currently available. We shall discuss these procedures in this chapter.