eff.aovlist              package:stats              R Documentation

Compute Efficiencies of Multistratum Analysis of Variance

Description:

     Computes the efficiencies of fixed-effect terms in an analysis of
     variance model with multiple strata.

Usage:

     eff.aovlist(aovlist)

Arguments:

 aovlist: The result of a call to 'aov' with an 'Error' term. 

Details:

     Fixed-effect terms in an analysis of variance model with multiple
     strata may be estimable in more than one stratum, in which case
     there is less than complete information in each. The efficiency is
     the fraction of the maximum possible precision (inverse variance)
     obtainable by estimating in just that stratum.

     This is used to pick strata in which to estimate terms in
     'model.tables.aovlist' and elsewhere.

Value:

     A matrix giving for each non-pure-error stratum (row) the
     efficiencies for each fixed-effect term in the model.

See Also:

     'aov', 'model.tables.aovlist', 'se.contrast.aovlist'

Examples:

     ## for balanced designs all efficiencies are zero or one.
     ## so as a statistically meaningless test:
     options(contrasts=c("contr.helmert", "contr.poly"))
     ## From Venables and Ripley (2002) p.165.
     N <- c(0,1,0,1,1,1,0,0,0,1,1,0,1,1,0,0,1,0,1,0,1,1,0,0)
     P <- c(1,1,0,0,0,1,0,1,1,1,0,0,0,1,0,1,1,0,0,1,0,1,1,0)
     K <- c(1,0,0,1,0,1,1,0,0,1,0,1,0,1,1,0,0,0,1,1,1,0,1,0)
     yield <- c(49.5,62.8,46.8,57.0,59.8,58.5,55.5,56.0,62.8,55.8,69.5,
     55.0, 62.0,48.8,45.5,44.2,52.0,51.5,49.8,48.8,57.2,59.0,53.2,56.0)

     npk <- data.frame(block=gl(6,4), N=factor(N), P=factor(P),
                       K=factor(K), yield=yield)
     npk.aovE <- aov(yield ~  N*P*K + Error(block), npk)
     eff.aovlist(npk.aovE)

