Liver tumor incidence — TCDD • drc

Liver tumor incidence in Sprague-Dawley rats exposed to the chemical like 2,3,7,8-tetrachlorodibenzo-pdioxin (TCDD).

Usage

data(TCDD)

Format

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

conc: a numeric vector reporting the concentration of TCDD (ng/kg)
total: a numeric vector
incidence: a numeric vector

Source

R. Kociba, D. Keyes, J. Beyer, R. Carreon, C. Wade, D. Dittenber, R. Kalnins, L. Frauson, C. Park, S. Barnard, R. Hummel, and C. Humiston (1978). Results of a two-year chronic toxicity and oncogenicity study of 2,3,7,8-tetrachlorodibenzo-p-dioxin in rats. Toxicology and Applied Pharmacology, 46(2):279–303.

Examples

library(drc)

## Displaying the data
head(TCDD)
#>    conc total incidence
#> 1  0.00    86         2
#> 2  1.55    50         1
#> 3  7.15    50         9
#> 4 38.56    45        14

## Fitting a two-parameter log-logistic model for binomial response
TCDD.m1 <- drm(incidence/total ~ conc, weights = total,
data = TCDD, fct = LL.2(), type = "binomial")
summary(TCDD.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) -0.73196    0.20589 -3.5551 0.0003778 ***
#> e:(Intercept) 96.49945   58.87278  1.6391 0.1011886    
#> ---
#> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

## Plotting the fitted curve
plot(TCDD.m1, xlab = "Concentration of TCDD (ng/kg)", ylab = "Tumor incidence")