agridat (version 1.12)

cochran.eelworms: Counts of eelworms before and after fumigant treatments

Description

Counts of eelworms before and after fumigant treatments

Format

A data frame with 48 observations on the following 7 variables.

block

Block factor, 4 levels

row

Row in field

col

Column in field

fumigant

Fumigant factor

dose

Dose. Numeric 0,1,2. Maybe should be a factor?

initial

Count of eelworms pre-treatment

final

Count of eelworms post-treatment

Details

In the original experiment plan (as shown in Bailey 2008), columns 9, 10, 11 are shifted up slightly.

Treatment codes: Con = Control, Chl = Chlorodinitrobenzen, Cym = Cymag, Car = Carbon Disulphide jelly, See = Seekay.

Experiment was conducted in 1935 at Rothamsted Experiment Station. In early March 400 grams of soil were sampled and the number of eelworm cysts were counted. Fumigants were added to the soil, oats were sown and later harvested. In October, the plots were again sampled and the final count of cysts recorded.

References

R. A. Bailey, 2008. Design of Comparative Experiments. Cambridge.

Examples

# NOT RUN {
data(cochran.eelworms)
dat <- cochran.eelworms

# Very strong spatial trends
desplot(initial ~ col*row, data=dat, flip=TRUE, main="cochran.eelworms")

# final counts are strongly related to initial counts
require(lattice)
xyplot(final~initial|dose, data=dat, group=fumigant,
       main="cochran.eelworms", xlab="Initial worm count",
       ylab="Final worm count", auto.key=list(columns=5))

# One approach...log transform, use 'initial' as covariate, create 9 treatments
dat <- transform(dat, trt=factor(paste0(fumigant, dose)))
m1 <- aov(log(final) ~ block + trt + log(initial), data=dat)
anova(m1)
# }