gomez.nonnormal1.Rd
Insecticide treatment effectiveness
data("gomez.nonnormal1")
A data frame with 36 observations on the following 3 variables.
trt
insecticidal treatment
rep
replicate
larvae
number of larvae
Nine treatments (including the control, T9) were used on four replicates. The number of living insect larvae were recorded.
The data show signs of non-normality, and a log transform was used by Gomez.
Gomez, K.A. and Gomez, A.A.. 1984, Statistical Procedures for Agricultural Research. Wiley-Interscience. Page 300.
Used with permission of Kwanchai Gomez.
None.
library(agridat) data(gomez.nonnormal1) dat <- gomez.nonnormal1 # Gomez figure 7.3 ## libs(dplyr) ## dat2 <- dat <!-- %>% group_by(trt) --> ## dat2 <- summarize(dat2, mn=mean(larvae), rng=diff(range(larvae))) ## plot(rng ~ mn, data=dat2, ## xlab="mean number of larvae", ylab="range of number of larvae", ## main="gomez.nonnormal1") # Because some of the original values are less than 10, # the transform used is log10(x+1) instead of log10(x). dat <- transform(dat, tlarvae=log10(larvae+1)) # QQ plots for raw/transformed data libs(reshape2, lattice) qqmath( ~ value|variable, data=melt(dat), main="gomez.nonnormal1 - raw/transformed QQ plot", scales=list(relation="free"))#>#> Analysis of Variance Table #> #> Response: tlarvae #> Df Sum Sq Mean Sq F value Pr(>F) #> rep 3 0.9567 0.31889 3.6511 0.0267223 * #> trt 8 3.9823 0.49779 5.6995 0.0004092 *** #> Residuals 24 2.0961 0.08734 #> --- #> Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1## Response: tlarvae ## Df Sum Sq Mean Sq F value Pr(>F) ## rep 3 0.9567 0.31889 3.6511 0.0267223 * ## trt 8 3.9823 0.49779 5.6995 0.0004092 *** ## Residuals 24 2.0961 0.08734