A note on the computation of the second-order derivatives of the elementary symmetric functions in the Rasch model (Q1088364)

\textit{P. G. W. Jansen} [Computing the second-order derivatives of the symmetric functions in the Rasch model. Kwantitatieve Methoden 5, 131-147 (1984)] gave explicit formulas for the computation of the second-order derivatives of the elementary symmetric functions. But they are only applicable to those pairs of items which have unequal parameters. It is shown here that for equal parameters similar explicit formulas do exist, too, facilitating the application of the Newton-Raphson procedure to estimate the parameters in the Rasch model and related models according to the conditional maximum likelihood principle.