Abstract: t-type regression estimators for the semiparametric nonlinear models were defined, and the EM algorithm for the t-type estimators were given. Moreover, the consistency of t-type regression estimators was obtained. And on the basis of the Q-function in the EM algorithm, statistical diagnostics methods were investigated. Finally, the proposed algorithm was tested by simulation analysis and by a real data sample.

Key words: nonlinear model, t-type regression estimator, Cook distance, local influence, penalized spline, EM algorithm, semiparametric regression, nonlinear model, t-type regression estimator, Cook distance, local influence, penalized spline, EM algorithm