gomez.nonnormal3 {agridat}

RCB experiment of rice, 12 varieties with leafhopper survival

Description

RCB experiment of rice, 12 varieties with leafhopper survival

Usage

data("gomez.nonnormal3")

Format

A data frame with 36 observations on the following 3 variables.

gen

genotype/variety of rice

rep

replicate

hoppers

percentage of surviving leafhoppers

Details

For each rice variety, 75 leafhoppers were caged and the percentage of surviving insects was determined.

Gomez suggest replacing 0 values by 1/(4*75) and replacing 100 by 1-1/(4*75) where 75 is the number of insects.

In effect, this means, for example, that (1/4)th of an insect survived.

Because the data are percents, Gomez suggested using the arcsin transformation.

Used with permission of Kwanchai Gomez.

Source

Gomez, K.A. and Gomez, A.A.. 1984, Statistical Procedures for Agricultural Research. Wiley-Interscience. Page 307.

References

None.

Examples

library(agridat)
data(gomez.nonnormal3)
dat <- gomez.nonnormal3

# First, replace 0, 100 values
dat$thoppers <- dat$hoppers
dat <- transform(dat, thoppers=ifelse(thoppers==0, 1/(4*75), thoppers))
dat <- transform(dat, thoppers=ifelse(thoppers==100, 100-1/(4*75), thoppers))
# Arcsin transformation of percentage p converted to degrees
# is arcsin(sqrt(p))/(pi/2)*90
dat <- transform(dat, thoppers=asin(sqrt(thoppers/100))/(pi/2)*90)

# QQ plots for raw/transformed data
libs(reshape2, lattice)
qqmath( ~ value|variable, data=melt(dat),
       main="gomez.nonnormal3 - raw/transformed QQ plot",
       scales=list(relation="free"))

m1 <- lm(thoppers ~ gen, data=dat)
anova(m1) # Match Gomez table 7.25
## Response: thoppers
##           Df  Sum Sq Mean Sq F value    Pr(>F)
## gen       11 16838.7 1530.79  16.502 1.316e-08 ***
## Residuals 24  2226.4   92.77