cochran.wireworms {agridat} | R Documentation |

##
Wireworms controlled by fumigants in a latin square

### Description

Wireworms controlled by fumigants in a latin square

### Format

A data frame with 25 observations on the following 4 variables.

`row`

row

`col`

column

`trt`

fumigant treatment, 5 levels

`worms`

count of wireworms per plot

### Details

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

### Source

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

### References

Ron Snee (1980). Graphical Display of Means.
*The American Statistician*, 34, 195-199.
https://www.jstor.org/stable/2684060
https://doi.org/10.1080/00031305.1980.10483028

W. Cochran (1940). The analysis of variance when experimental errors
follow the Poisson or binomial laws.
*The Annals of Mathematical Statistics*, 11, 335-347.
https://www.jstor.org/stable/2235680

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

### Examples

## Not run:
library(agridat)
data(cochran.wireworms)
dat <- cochran.wireworms
libs(desplot)
desplot(dat, worms ~ col*row,
text=trt, cex=1, # aspect unknown
main="cochran.wireworms")
# Trt K is effective, but not the others. Really, this says it all.
libs(lattice)
bwplot(worms ~ trt, dat, main="cochran.wireworms", xlab="Treatment")
# 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.
libs(lme4)
m3 <- glmer(worms ~ -1 +trt +(1|rowf) +(1|colf), data=dat, family="poisson")
summary(m3)
## Fixed effects:
## Estimate Std. Error z value Pr(>|z|)
## trtK 0.1393 0.4275 0.326 0.745
## trtM 1.7814 0.2226 8.002 1.22e-15 ***
## trtN 1.9028 0.2142 8.881 < 2e-16 ***
## trtO 1.7147 0.2275 7.537 4.80e-14 ***
## End(Not run)

[Package

*agridat* version 1.18

Index]