RCB experiment of rice, measuring white heads

data("gomez.nonnormal2")

Format

A data frame with 42 observations on the following 3 variables.

gen: genotype
rep: replicate
white: percentage of white heads

Details

The data are the percent of white heads from a rice variety trial of 14 varieties with 3 reps. Because many of the values are less than 10, the suggested data transformation is sqrt(x+.5).

Source

Gomez, K.A. and Gomez, A.A.. 1984, Statistical Procedures for Agricultural Research. Wiley-Interscience. Page 300.

Used with permission of Kwanchai Gomez.

References

None.

Examples


library(agridat)

data(gomez.nonnormal2)
dat <- gomez.nonnormal2

# Gomez suggested sqrt transform
dat <- transform(dat, twhite = sqrt(white+.5))

# QQ plots for raw/transformed data
libs(reshape2, lattice)
qqmath( ~ value|variable, data=melt(dat),
       main="gomez.nonnormal2 - raw/transformed QQ plot",
       scales=list(relation="free"))
#> Using gen, rep as id variables

# Gomez anova table 7.21
m1 <- lm(twhite ~ rep + gen, data=dat)
anova(m1)
#> Analysis of Variance Table
#> 
#> Response: twhite
#>           Df Sum Sq Mean Sq F value    Pr(>F)    
#> rep        2  2.401  1.2004  1.9137    0.1678    
#> gen       13 48.011  3.6931  5.8877 6.366e-05 ***
#> Residuals 26 16.309  0.6273                      
#> ---
#> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## Response: twhite2
##           Df Sum Sq Mean Sq F value    Pr(>F)    
## rep        2  2.401  1.2004  1.9137    0.1678    
## gen       13 48.011  3.6931  5.8877 6.366e-05 ***
## Residuals 26 16.309  0.6273