Infections as response to exposure with Echovirus 12

For each of four doses of a pathogen, Echovirus 12, the number of exposed and infected human volunteers are reported.

Usage

data(echovirus)

Format

A data frame with 4 observations on the following 3 variables.

dose: a numeric vector reporting the dose in plague forming units (pfu)
total: a numeric vector
infected: a numeric vector

Source

H. Moon, S. B. Kim, J. J. Chen, N. I. George, and R. L. Kodell (2013). Model uncertainty and model averaging in the estimation of infectious doses for microbial pathogens. Risk Analysis, 33(2):220-231.

Examples

library(drc)

## Displaying the data
head(echovirus)
#>    dose total infected
#> 1   330    50       15
#> 2  1000    20        9
#> 3  3300    26       19
#> 4 10000    12       12

## Fitting a two-parameter log-logistic model for binomial response
echovirus.m1 <- drm(infected/total ~ dose, weights = total,
data = echovirus, fct = LL.2(), type = "binomial")
summary(echovirus.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)  -0.94621    0.20507 -4.6141 3.948e-06 ***
#> e:(Intercept) 921.04805  215.00279  4.2839 1.837e-05 ***
#> ---
#> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

## Plotting the fitted curve
plot(echovirus.m1, xlab = "Dose (pfu)", ylab = "Proportion infected")