drc (version 1.6-1)

finney71: Example from Finney (1971)

Description

For each of six concentration of an insecticid the number of insects affected (out of the number of insects) was recorded.

Usage

data(finney71)

source

Finney, D. J. (1971) Probit Analysis, Cambridge: Cambridge University Press.

Examples

## Model with ED50 as a parameter
finney71.m1 <- drm(affected/total~dose, weights=total,
data=finney71, fct=LL.2(), type="binomial")

summary(finney71.m1)
plot(finney71.m1, conLevel = 0.1, broken=TRUE, lwd = 2)

ED(finney71.m1, c(10, 20, 50), ci="delta", reference="control")

## Model fitted with 'glm'
#fitl.glm <- glm(cbind(affected, total-affected) ~ log(dose),
#family=binomial(link = logit), data=finney71[finney71$dose != 0, ])
#summary(fitl.glm)  # p-value almost agree for the b parameter
#
#xp <- dose.p(fitl.glm, p=c(0.50, 0.90, 0.95))  # from MASS
#xp.ci <- xp + attr(xp, "SE") %*% matrix(qnorm(1 - 0.05/2)*c(-1,1), nrow=1)
#zp.est <- exp(cbind(xp.ci[,1],xp,xp.ci[,2]))
#dimnames(zp.est)[[2]] <- c("zp.lcl","zp","zp.ucl")
#zp.est  # not far from above results with 'ED'

## Model with log(ED50) as a parameter
finney71.m2 <- drm(affected/total~dose, weights=total,
data=finney71, fct=LL2.2(), type="binomial")

## Confidence intervals based on back-transformation
##  complete agreement with results based on 'glm'
ED(finney71.m2, c(10, 20, 50), ci="fls", reference="control")