It has previously been shown that the Bock-Aitkin procedure (R. Bock and M. Aitkin, 1981) is an instance of the EM algorithm when trying to find the marginal maximum likelihood estimate for a discrete latent ability variable (latent trait). In this paper, it is shown that the Bock-Aitkin procedure is a numerical implementation of the EM algorithm for a continuous latent ability variable using numerical quadrature. Further, the relationship between the EM algorithm, marginal maximum likelihood estimation, and the Bock-Aitkin procedure is described for both the discrete and continuous cases. Some issues concerning the use of the Bock-Aitkin procedure and the EM algorithm are addressed. (Contains 31 references.) (SLD)