Strip-split-plot of barley with fertilizer, calcium, and soil factors.

Format

A data frame with 96 observations on the following 5 variables.

rep: replicate, 4 levels
soil: soil, 3 levels
fert: fertilizer, 4 levels
calcium: calcium, 2 levels
yield: yield of winter barley

Details

Four different fertilizer treatments are laid out in vertical strips, which are then split into subplots with different levels of calcium. Soil type is stripped across the split-plot experiment, and the entire experiment is then replicated three times.

Sometimes called a split-block design.

Source

Comes from the notes of Gertrude Cox and A. Rotti.

References

SAS/STAT(R) 9.2 User's Guide, Second Edition. Example 23.5 Strip-Split Plot. https://support.sas.com/documentation/cdl/en/statug/63033/HTML/default/viewer.htm#statug_anova_sect030.htm

Examples

if (FALSE) { # \dontrun{

library(agridat)
data(cox.stripsplit)
dat <- cox.stripsplit

# Raw means
# aggregate(yield ~ calcium, data=dat, mean)
# aggregate(yield ~ soil, data=dat, mean)
# aggregate(yield ~ calcium, data=dat, mean)

libs(HH)
interaction2wt(yield ~ rep + soil + fert + calcium, dat,
               x.between=0, y.between=0,
               main="cox.stripsplit")

# Traditional AOV
m1 <- aov(yield~ fert*calcium*soil +
          Error(rep/(fert+soil+calcium:fert+soil:fert)),
          data=dat)
summary(m1)

# With balanced data, the following are all basically identical

libs(lme4)
# The 'rep:soil:fert' term causes problems...so we drop it.
m2 <- lmer(yield ~ fert*soil*calcium + (1|rep) + (1|rep:fert) +
             (1|rep:soil) + (1|rep:fert:calcium), data=dat)


if(0){
  # afex uses Kenword-Rogers approach for denominator d.f.
  libs(afex)
  mixed(yield ~ fert*soil*calcium + (1|rep) + (1|rep:fert) +
          (1|rep:soil) + (1|rep:fert:calcium) + (1|rep:soil:fert), data=dat,
        control=lmerControl(check.nobs.vs.rankZ="ignore"))
  ##              Effect      stat ndf     ddf F.scaling p.value
  ## 1       (Intercept) 1350.8113   1  3.0009         1  0.0000
  ## 2              fert    3.5619   3  9.0000         1  0.0604
  ## 3              soil    3.4659   2  6.0000         1  0.0999
  ## 4           calcium    1.8835   1 12.0000         1  0.1950
  ## 5         fert:soil    1.2735   6 18.0000         1  0.3179
  ## 6      fert:calcium    4.4457   3 12.0000         1  0.0255
  ## 7      soil:calcium    0.2494   2 24.0000         1  0.7813
  ## 8 fert:soil:calcium    0.3504   6 24.0000         1  0.9027
}

} # }