Effect of Insecticide on survivial of tobacco budworms

Description

number of killed budworms exposed 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 [mug]

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))





## Not run: 
* SAS example;
data budworm;
infile 'budworm.txt' firstobs=2;
input sex dose ndead ntotal;
run;

## End(Not run)

Results