Weight gain for different methionine sources

Data consist of average body weight gain of chickens being treated with one of the two methionine sources DLM and HMTBA.

Usage

data(methionine)

Format

A data frame with 9 observations on the following 3 variables:

product: a factor with levels control, DLM and MHA denoting the treatments
dose: a numeric vector of methionine dose
gain: a numeric vector of average body weight gain

Details

The dataset contains a common control measurement for the two treatments.

Source

Kratzer. D. D. and Littell, R. C. (2006) Appropriate Statistical Methods to Compare Dose Responses of Methionine Sources, Poultry Science, 85, 947–954.

Examples

library(drc)

## Fitting model with constraint on one parameter 
met.ar.m1 <- drm(gain~dose, product, data = methionine, 
fct = AR.3(), pmodels = list(~1, ~factor(product), ~factor(product)), 
upperl = c(Inf, Inf, 1700, Inf, Inf)) 
#> Control measurements detected for level: control

plot(met.ar.m1, xlim=c(0,0.3), ylim=c(1450, 1800))
abline(h=1700, lty=1)


summary(met.ar.m1)
#> 
#> Model fitted: Shifted asymptotic regression (3 parms)
#> 
#> Parameter estimates:
#> 
#>                 Estimate Std. Error t-value   p-value    
#> c:(Intercept) 1.4483e+03 2.1249e+01 68.1582 2.776e-07 ***
#> d:DLM         1.6887e+03 1.9221e+01 87.8589 1.006e-07 ***
#> d:MHA         1.7000e+03 2.0773e+01 81.8359 1.336e-07 ***
#> e:DLM         4.4217e-02 1.4050e-02  3.1472   0.03461 *  
#> e:MHA         5.9462e-02 1.4529e-02  4.0925   0.01494 *  
#> ---
#> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
#> 
#> Residual standard error:
#> 
#>  22.32469 (4 degrees of freedom)