finney71 {drc} | R Documentation |
For each of six concentration of an insecticid the number of insects affected (out of the number of insects) was recorded.
data(finney71)
A data frame with 6 observations on the following 3 variables.
dose
total
affected
Finney, D. J. (1971) Probit Analysis, Cambridge: Cambridge University Press.
## 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") #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")