Chapter 6 Exercises
Beetles

1. Run the code for the Beetles dose-response analysis from Example 6.5.1 with
centered doses of carbon disulphide. Create two sets of initial values so that a two-chain analysis can be performed. When do the chains converge? And what is the degree of autocorrelation in the chains? Select "Correlations" from the "Inference" menu and create a scatter-plot of alpha vs beta to examine their posterior correlation [Hint: don't use too many samples as this plot requires a substantial amount of memory.]

2. Adapt the code to run the analysis with
un-centred doses of carbon disulphide. What is the impact on convergence, autocorrelation, and posterior correlation between alpha and beta?

3. Try fitting probit versions of the centred model, using both the probit link and the phi function [note that these can be sensitive to initial values] . Is the model fit visually different compared to the logistic model?