this paper we propose a modification to the methods used to motivate many information and posterior probability criteria for the weighted likelihood case. We derive weighted versions for two of the most widely known criteria, namely the AIC and BIC. Via a simple modification, the criteria are also made useful for window span selection. The usefulness of the weighted version of these criteria are demonstrated through a simulation study and an application to three data sets. KEY WORDS: Information Criteria; Posterior Probability Criteria; Model Selection; Local Likelihood. 1. INTRODUCTION Local regression has become a popular method for smoothing scatterplots and for nonparametric regression in general. It has proven to be a useful tool in finding structure in datasets (Cleveland and Devlin 1988). Local regression estimation is a method for smoothing scatterplots (x i ; y i ), i = 1; : : : ; n in which the fitted value at x 0 is the value of a polynomial fit to the data using weighted least squares where the weight given to (x i ; y i ) is related to the distance between x i and x 0 . Stone (1977) shows that estimates obtained using the local regression methods have desirable theoretical properties. Recently, Fan (1993) has studied minimax properties of local linear regression. Tibshirani and Hastie (1987) extend the ideas of local regression to a local likelihood procedure. This procedure is designed for nonparametric regression modeling in situations where weighted least squares is inappropriate as an estimation method, for example binary data. Local regression may be viewed as a special case of local likelihood estimation. Tibshirani and Hastie (1987), Staniswalis (1989), and Loader (1999) apply local likelihood estimation to several types of data where local regressio...

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