The two data sets are PCB1 and PCB2. In both data files the response variate is the concentration of polychlorinated biphenyl (PCB) residue in fish (Yellowfin Bream) caught from two different lakes. The PCB1 measurements are from homebush lake and the PCB2 measurements are from swan lake.
For both data sets the explanatory variable is the age of the fish. The PCB measurements are in mg per kg of fish body weight. As the fish in the lake were stocked as yearlings, and tagged at release, their age is known. To obtain a measure of the PCB concentration in the fish lethal methods were required. The fish vary in age from one year to 12 years. The relationship of interest is whether or not the PCB concentration in the fish increases the longer they have been in the lake. Specifically, both lakes are known sites of PCB contamination. However, it is thought that the PCBs may settle over time and be covered with sediment. If the PCBs settle to the bottom of the lake and are covered by sediment, there should be no relationship between fish age and the PCB concentration in the fish sampled. If the PCBs are still present in the water then the PCB concentration in the fish will increase with fish age. The environmental safe level for PBC concentrations is deemed to be 0.5 mg per kg of fish weight.
The State government has employed you to prepare a report on the relationship between the PCB concentration and fish age in the two lakes, and to provide an assessment of overall PCB safety at each lake, based on your assessment of PC concentration in the fish.
For this assignment you do not need to source additional references. The question focuses on writing simplified responses in the format of scientific papers, which in this instance will be: Introduction, Methods and Data, Results, and Discussion. The Assignment is a capstone assessment where you are required to bring together your knowledge of the regression model and scientific writing. The content of each section of your assignment report should be as described below:
Introduction – a simple overview statement of the nature of the experiment. This can largely be a rephrasing of the detail I provide to explain the question context. You are not expected to do any primary research on the topic to write the introduction.
Methods and Data – as you will be using data sets provided you do not need to make any statements about the method used to collect data. Rather, you need to include statements related to the approach/ steps used for data analysis. This includes formal statements about what tests you are conducting, the null and alternate hypothesis, the alpha level used, etc. Also think about how to incorporate an effective data summary table in this section.
Results – this section will contain summary table(s) for the testing you have conducted/ models you have estimated. You also need to include very brief summary statements that explain how the results should be interpreted.
Discussion – this is the section that allows you to demonstrate a high level of understanding of what you have done. As per the introduction, you are not expected to demonstrate specific knowledge of PCBs, but rather an understanding of the modelling process and the ability to interpret results.
Conclusion – this is a very short statement that covers your key finding from the research you have conducted. It is the punchy end to the report. The take home message.
Use of sub-headings – there are two related data sets on PCB concentrations in Fish at two different locations. As such, you may wish to use sub-headings in some sections.
The assignment is about data presentation and explaining the process of investigation. Visual plots are an essential part of any answer, so make an effort to get your plots looking nice. They also must reproduce as high quality images. Think metafile format if using a PC and pdf format if using a mac. Think hard about the different types of plots you can generate, and the specific visual representations that would be of value, and any limitations of a specific plot, given your final conclusions. All figures and tables must have appropriate caption labels. Also think hard about how you might use a table format to assist in presenting information. As a guide to the standard required for tables and figures look at the production standard in some journal articles. Also follow the journal practice of providing plots that reproduce clearly in black and white. Tables might have a structure like that shown below. Do not report Standard Errors, and p-values, and t-values. These three sets of measures contain the same information, so just report one set of values. Convention differs by discipline, but the convention for fisheries and environmental management, which is the context for the assignment, is to use standard error information for regression summary results tables. If there is something non-standard about the standard errors, for example the use of heteroskedastic or heteroskedastic and autocorrelation robust standard errors, then this additional information can be added as a note below the table. Table captions must be above the table. Figure captions can be either above or below the Figure. Do not feel compelled to have figures stretch across the entire page. It is fine to leave white space on the right hand side of the page, or centre figures and have white space on both the left and right of the figure.