Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:These properties have been noticed by others who used ̂κ in place of ̂ (Friedman 1989; Brown et al. 1999), and they can be exploited to reduce the computation time for regularized discriminant analysis in high-dimensional settings (Hastie and Tibshirani 2004). • R̂λ can be calculated by multiplying all off-diagonal elements of R̂ by λ. • The proposed regularization will reduce the bias inherent in eigenvalues of sample correlation matrices (Friedman 1989), provided that a reasonable choice of regularization parameter λ is used. Bias generally will not be completely removed. • R̂λ manages a bias–variance trade-off; R̂ has potentially high variance but relatively little bias (being asymptotically unbiased for large N , fixed p), and I has no variance, but is biased for R in general. Thus, loosely speaking, R̂λ can be thought of as a weighted average of a variance term and a bias term, and we aim to choose λ to optimize this bias–variance trade-off. Ledoit and Wolf (2004) previously made this point for ̂κ .
Category: