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Table 1 Summary of variance shrinkage used by several procedures

From: A benchmark for statistical microarray data analysis that preserves actual biological and technical variance

Method

Equation

Shrinkage level

Offset Estimation

Regularized t-test

V = S2

Window Estimator

SAM d-statistic (Tusher)

a = 1

b = 1

V = S

S0 = arg min(CV(MAD(d a )))

Fudge factor minimizing CV

Moderated-t (Limma)

V = S2

ψ, ψ' = digamma, trigamma functions

Shrinkage-t

b = 1 - a

V = S2

  1. The general formulation V = a V0 + b Vg illustrates that the variability estimator is estimated from two terms, respectively the background variability V0 and individual variability Vg.