chlorac

Data from an acute toxicity test where organisms were exposed to different concentrations of chloroacetaldehyde. The number of dead subjects out of a total were recorded for each concentration.

Usage

data(chlorac)

Format

A data frame with 6 observations on the following 3 variables.

conc

a numeric vector

total

a numeric vector

num.dead

a numeric vector

Examples

library(drc)

## Displaying the data
head(chlorac)
#>   conc total num.dead
#> 1    0    40        3
#> 2   10    40        5
#> 3   20    40        6
#> 4   40    40       38
#> 5   80    40       40
#> 6  160    40       40

## Fitting a two-parameter log-logistic model for binomial response
chlorac.m1 <- drm(num.dead/total ~ conc, weights = total,
data = chlorac, fct = LL.2(), type = "binomial")
summary(chlorac.m1)
#> 
#> Model fitted: Log-logistic (ED50 as parameter) with lower limit at 0 and upper limit at 1 (2 parms)
#> 
#> Parameter estimates:
#> 
#>               Estimate Std. Error t-value   p-value    
#> b:(Intercept)  -3.8861     0.5787 -6.7152 1.878e-11 ***
#> e:(Intercept)  24.1102     1.6173 14.9082 < 2.2e-16 ***
#> ---
#> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

## Plotting the fitted curve
plot(chlorac.m1, xlab = "Concentration", ylab = "Proportion dead")