multcomp (version 1.2-12)

litter: Litter Weights Data Set

Description

Dose response of litter weights in rats.

Usage

data("litter")

source

P. H. Westfall, R. D. Tobias, D. Rom, R. D. Wolfinger, Y. Hochberg (1999). Multiple Comparisons and Multiple Tests Using the SAS System. Cary, NC: SAS Institute Inc., page 109.

P. H. Westfall (1997). Multiple Testing of General Contrasts Using Logical Constraints and Correlations. Journal of the American Statistical Association, 92(437), 299--306.

Details

Pregnant mice were divided into four groups and the compound in four different doses was administered during pregnancy. Their litters were evaluated for birth weights.

Examples

### fit ANCOVA model to data
  amod <- aov(weight ~ dose + gesttime + number, data = litter)

  ### define matrix of linear hypotheses for `dose'
  doselev <- as.integer(levels(litter$dose))
  K <- rbind(contrMat(table(litter$dose), "Tukey"),
             otrend = c(-1.5, -0.5, 0.5, 1.5),
             atrend = doselev - mean(doselev),
             ltrend = log(1:4) - mean(log(1:4)))

  ### set up multiple comparison object
  Kht <- glht(amod, linfct = mcp(dose = K), alternative = "less")

  ### cf. Westfall (1997, Table 2)
  summary(Kht, test = univariate())
  summary(Kht, test = adjusted("bonferroni"))
  summary(Kht, test = adjusted("Shaffer"))
  summary(Kht, test = adjusted("Westfall"))
  summary(Kht, test = adjusted("single-step"))