H.virescens | R Documentation |

## Mortality of tobacco budworms

### Description

For three days, moths of the tobacco budworm (*Heliothis virescens*) were exposed
to doses of the pyrethroid trans-cypermethrin.

### Usage

data(H.virescens)

### Format

A data frame with 12 observations on the following 4 variables.

`dose`

a numeric vector of dose values (*μ g*)

`numdead`

a numeric vector of dead or knocked-down moths

`total`

a numeric vector of total number of moths

`sex`

a factor with levels `F`

`M`

denoting a grouping according to sex

### Details

In Venables and Ripley (2002), these data are analysed using a logistic regression with base-2 logarithm of dose
as explanatory variable.

### Source

Venables, W. N. and Ripley, B. D (2002) *Modern Applied Statistics with S*, New York: Springer (fourth edition).

### Examples

## Fitting dose-response model (log-logistic with common slope)
Hv.m1 <- drm(numdead/total~dose, sex, weights = total, data = H.virescens, fct = LL.2(),
pmodels = list(~ 1, ~ sex - 1), type = "binomial")
summary(Hv.m1)
## Fitting the same model as in Venables and Riply (2002)
Hv.m2 <- glm(cbind(numdead, total-numdead) ~ sex + I(log2(dose)) - 1, data = H.virescens,
family = binomial)
## Comparing the fits
logLik(Hv.m1)
logLik(Hv.m2)
## Estimated ED values (matching those given in MASS)
ED(Hv.m1, c(25, 50, 75))