gomez.nonnormal3: RCB of 12 rice varieties with leafhopper survival

Description Usage Format Details Source References Examples

Description

RCB of 12 rice varieties with leafhopper survival

Usage

1
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.

Source

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

Used with permission of Kwanchai Gomez.

References

None.

Examples

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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
if(require(reshape2) & require(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                      

agridat documentation built on May 2, 2019, 4:01 p.m.