Chlordan

Data from a chronic toxicity test measuring the reproduction of Daphnia exposed to different concentrations of chlordane at two time points. The response measured was the number of offspring (repro) per replicate.

Usage

data(chlordan)

Format

A data frame with 60 observations on the following 5 variables.

replicate

a numeric vector

conc

a numeric vector

repro

a numeric vector

time

a numeric vector

Examples

library(drc)

## Displaying the data
head(chlordan)
#>   replicate conc repro time
#> 1         1 0.00   125 21.0
#> 2         1 0.18    89 21.0
#> 3         1 0.73    90 21.0
#> 4         1 1.82    42 21.0
#> 5         1 2.90    29 21.0
#> 6         1 7.00    10 11.5

## Fitting a three-parameter log-logistic model
chlordan.m1 <- drm(repro ~ conc, data = chlordan, fct = LL.3())
summary(chlordan.m1)
#> 
#> Model fitted: Log-logistic (ED50 as parameter) with lower limit at 0 (3 parms)
#> 
#> Parameter estimates:
#> 
#>                Estimate Std. Error t-value   p-value    
#> b:(Intercept)   1.00663    0.14921  6.7463 8.414e-09 ***
#> d:(Intercept) 115.12320    5.05139 22.7904 < 2.2e-16 ***
#> e:(Intercept)   1.55178    0.24368  6.3681 3.565e-08 ***
#> ---
#> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
#> 
#> Residual standard error:
#> 
#>  16.86007 (57 degrees of freedom)

## Plotting the fitted curve
plot(chlordan.m1, xlab = "Concentration", ylab = "Reproduction")