Modified Latin Square experiments of wheat

Modified Latin Square experiments of wheat for two varieties and 2 years

Usage

data("riddle.wheat")

Format

A data frame with 650 observations on the following 7 variables.

expt: experiment
strain: strain
rep: replicate
row: row (nested in column)
year: year
yield: yield, grams
col: column (group of rows)

Details

There was an experiment for "Baart" varieties in 1939 and another experiment for "White Federation" varieties in 1939. The experiments were repeated in 1940.

The experimental design is a Modified Latin Square. There are 5 reps, horizontal. There are 5 "columns". Each rep*column contains multiple plots Each strain is planted in a 16-foot row.

Field length: 5 reps * 16 feet

Field width: 25 or 30 rows, perhaps 0.5 feet between rows

Riddle & Baker note: Two strains, 5129 (Baart) and 1617 (White Federation) reversed their position from significantly LOWER in 1939 to significantly HIGHER than the general mean in 1940.

Source

Riddle, O. C. and G. A. Baker. (1944). Biases encountered in large-scale yield tests. Hilgardia, 16, 1-14. https://doi.org/10.3733/hilg.v16n01p001

References

None

Examples

if (FALSE) { # \dontrun{
  library(agridat)
  data(riddle.wheat)
  dat <- riddle.wheat

  datb39 <- subset(dat, expt=="Baart" & year==1939)
  datb40 <- subset(dat, expt=="Baart" & year==1940)
  datw39 <- subset(dat, expt=="WhiteFed" & year==1939)
  datw40 <- subset(dat, expt=="WhiteFed" & year==1940)
  # Match table 4, sections a, b, d, e
  anova(aov(yield ~ factor(rep) + factor(col) + strain, datb39))
  anova(aov(yield ~ factor(rep) + factor(col) + strain, datb40))
  anova(aov(yield ~ factor(rep) + factor(col) + strain, datw39))
  anova(aov(yield ~ factor(rep) + factor(col) + strain, datw40))

  libs(desplot)
  # Show the huge variaion between reps
  dat$yrexpt <- paste0(dat$year, dat$expt)
  desplot(dat, yield ~ row*rep|yrexpt, tick=TRUE, out1=col, main="riddle.wheat",
          aspect=(5*16)/(30*.5))
# Show the randomization was the same in each year (but not each expt).
desplot(dat, strain ~ row*rep|yrexpt, tick=TRUE, out1=col, main="riddle.wheat")

} # }