Tamer Mohamed Elsaid Elbayoumi
Department of Statistics
Western Michigan University
A weighted L1 (WL1) estimate for estimating the parameters of the BAR model is considered. When the weights are constant, the estimate is equivalent to the least absolute deviation estimate (L1). The estimate is shown to be asymptotically normal. Simulated, artificial, and actual examples are presented and it is shown that the unweighted and weighted L1–based estimates are capable of coping with certain kinds of outliers in both response and factor spaces. These estimates, as well as others (e.g. weighted Wilcoxon estimates) are studied via Monte Carlo. Models include both innovation outlier (IO) and additive outlier (AO) models as well as a variety of correlation structures.
Overall, most of the estimates perform quite well under a variety of situations. However, no one estimate is superior to the others and the superiority of the estimates depends on the underlying probability model. These findings are consistent with findings in the literature pertaining to autoregressive (AR) time series models.
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