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The estimation of prediction error: Covariance penalties and cross-validation. (English) Zbl 1117.62324
Summary: Having constructed a data-based estimation rule, perhaps a logistic regression or a classification tree, the statistician would like to know its performance as a predictor of future cases. There are two main theories concerning prediction error: (1) penalty methods such as C p , Akaike’s information criterion, and Stein’s unbiased risk estimate that depend on the covariance between data points and their corresponding predictions; and (2) cross-validation and related nonparametric bootstrap techniques. This article concerns the connection between the two theories. A Rao-Blackwell type of relation is derived in which nonparametric methods such as cross-validation are seen to be randomized versions of their covariance penalty counterparts. The model-based penalty methods offer substantially better accuracy, assuming that the model is believable.
62-99Statistics (MSC2000)