agridat (version 1.5)

cochran.wireworms: Wireworms controlled by fumigants in a latin square

Description

Wireworms controlled by fumigants in a latin square

Usage

data(cochran.wireworms)

source

W. G. Cochran (1938). Some difficulties in the statistical analysis of replicated experiments. Empire Journal of Experimental Agriculture, 6, 157--175.

Details

Plots were approximately 22cm by 13cm. Layout of the experiment was a latin square. The number of wireworms in each plot was counted, following soil fumigation the previous year.

References

G W Snedecor and W G Cochran, 1980. Statistical Methods, Iowa State University Press. Page 288.

Examples

dat <- cochran.wireworms

# Trt K is effective, but not the others.  Really, this says it all.
bwplot(worms ~ trt, dat)

# Snedecor and Cochran do ANOVA on sqrt(x+1).
dat <- transform(dat, rowf=factor(row), colf=factor(col))
m1 <- aov(sqrt(worms+1) ~ rowf + colf + trt, data=dat)
anova(m1)

# Instead of transforming, use glm
m2 <- glm(worms ~ trt + rowf + colf, data=dat, family="poisson")
anova(m2)

# GLM with random blocking.
require(lme4)
m3 <- lmer(worms ~ -1 + trt + (1|rowf) + (1|colf),
           data=dat, family="poisson")
summary(m3)