gomez.nonnormal3 {agridat} | R Documentation

## RCB of 12 rice varieties with leafhopper survival

### Description

RCB of 12 rice 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.

### 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

    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

[Package agridat version 1.16 Index]