Since the items have been calibrated, the item parameters are assumed to
be known. A Gaussian quadrature procedure can be applied to obtain maximum
likelihood estimates of the ability parameter (ABRAMOWITZ; STENGUN, 1964). It
should be noted that maximum likelihood estimates stay undetermined until a
mixed response pattern is observed. As an alternative the Warm estimator (WARM,
1989) can be applied, where a weighted likelihood is maximized.