Effect of Insecticide on survivial of tobacco budworms

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

Details

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

Source

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

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))