doBy (version 4.5-15)

budworm: Effect of Insecticide on survivial of tobacco budworms

Description

Number of killed budworms after exposure to an insecticide.

Usage

data(budworm)

Format

This data frame contains 12 rows and 4 columns:

sex:

sex of the budworm

dose:

dose of the insecticide trans-cypermethrin in $micro g$

ndead:

budworms killed in a trial

ntotal:

total number of budworms exposed per trial

Source

Collet, D. (1991) Modelling Binary Data, Chapman & Hall, London, Example 3.7

Details

Mortality of the moth tobacco budworm 'Heliothis virescens' for 6 doses of the pyrethroid trans-cypermethrin differentiated with respect to sex.

References

Venables, W.N; Ripley, B.D.(1999) Modern Applied Statistics with S-Plus, Heidelberg, Springer, 3rd edition, chapter 7.2

Examples

data(budworm)
## function to caclulate the empirical logits
empirical.logit<- function(nevent,ntotal) {
  y<-log ((nevent+0.5)/(ntotal-nevent+0.5))
  y
}

## plot the empirical logits against log-dose

log.dose  <- log(budworm$dose)
emp.logit <- empirical.logit(budworm$ndead,budworm$ntotal)
plot(log.dose,emp.logit,type='n',xlab='log-dose',ylab='emprirical logit')
title('budworm: emprirical logits of probability to die ')

male   <- budworm$sex=='male'
female <- budworm$sex=='female'
lines(log.dose[male],emp.logit[male],type='b',lty=1,col=1)
lines(log.dose[female],emp.logit[female],type='b',lty=2,col=2)
legend(0.5,2,legend=c('male','female'),lty=c(1,2),col=c(1,2))