Due Friday, October 6
- Do problem 16 from the Problems of Proportions handout.
- One way to measure concentrations of trace elements is to measure accumulation in animals. For example, the fish data contains information on mercury concentrations in fish in North Carolina rivers. Suppose we are interested in comparing the proportion of fish with mercury concentration greater than 1.0 ppm by location (measuring station). For now, we will only use columns 2 and 5. Analyze the data as follows:
- Read in the data and create a dummy variable for mercury concentration ( > 1.0 ppm vs. <= 1.0 ppm).
- Create a vector of total counts by station, and a vector of counts of fish with large mercury concentration by station (these are your n and y binomial data; you may want to use the tabulate command for this).
- Create an error.bar plot and comment on it.
- Analyze the posterior for the rankings and describe your findings.