Offsprings resulting from a toxicity test

Results from a chronic reproduction toxicity test with seven different concentrations of waste water. The response was the number of offspring produced by the water flea Ceriodaphnia dubia.

Usage

data(C.dubia)

Format

A data frame with 50 observations of the following 2 variables.

conc

a numeric vector giving waste water in percentage

number

a numeric vector

Source

A. J. Bailer and J. T. Oris (1997). Estimating inhibition concentrations for different response scales using generalized linear models. Environmental Toxicology and Chemistry, 16:1554–1559.

Examples

library(drc)

## Displaying the data
head(C.dubia)
#>   conc number
#> 1    0     27
#> 2    0     30
#> 3    0     29
#> 4    0     31
#> 5    0     16
#> 6    0     15

## Fitting a three-parameter log-logistic model
C.dubia.m1 <- drm(number ~ conc, data = C.dubia, fct = LL.3())
summary(C.dubia.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)  16.1372    61.8281  0.2610    0.7952    
#> d:(Intercept)  28.7500     1.1123 25.8464 < 2.2e-16 ***
#> e:(Intercept)  11.9536     2.0608  5.8004  5.39e-07 ***
#> ---
#> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
#> 
#> Residual standard error:
#> 
#>  7.03479 (47 degrees of freedom)

## Plotting fitted curve together with the original data
plot(C.dubia.m1, xlab = "Concentration (%)", ylab = "Number of offspring")