Detergent Durability Data Set

Description

Detergent durability in an incomplete two-way design.

Usage

data("detergent")

Format

This data frame contains the following variables

detergent

detergent, a factor at levels A, B, C, D, and E.

block

block, a factor at levels B_1, ..., B_10.

plates

response variable: number of plates washed before the foam disappears.

Details

Plates were washed with five detergent varieties, in ten blocks. A complete design would have 50 combinations, here only three detergent varieties in each block were applied in a balanced incomplete block design. Note that there are six observations taken at each detergent level. The data were published by Westfall, Tobias, Rom, Wolfinger, and Hochberg (1999).

References

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

Examples

  ### set up two-way ANOVA without interactions
  amod <- aov(plates ~ block + detergent, data = detergent)

  ### set up all-pair comparisons
  dht <- glht(amod, linfct = mcp(detergent = "Tukey"))

  ### see Westfall et al. (1999, p. 190)
  confint(dht)

  ### see Westfall et al. (1999, p. 192)
  summary(dht, test = univariate())
  ## Not run: 
  summary(dht, test = adjusted("Shaffer"))
  summary(dht, test = adjusted("Westfall"))
  
## End(Not run)