Length-biased sampling is frequently a convenient technique for the collectionof positive or lifetime data.Right censoring may affect the sampled information due totime limitation in following-up or loss to follow up.For length-biased data,Wang (1996) developed semiparametricestimation procedures for the proportional hazards model.In this article,for length-biased and right-censored data, we constructsemiparametric estimation proceduresfor proportional and additive hazards models.Simulation results show that semiparametric estimatorscan outperform nonparametric estimators when censoringis not heavy and truncation is severe.
