By Support


  • This assignment consists of 7 questions meant to provide practice with the material that will have been covered between May 11th and May 17th.
  • You may complete the assignment in one of the following formats: MS Word, PDF, plain text, or a single file containing a high-quality scan of your hand-written assignment text (regrettably, we do not have the ability to read “pages” or ”Google Docs” formats). If you are unsure about the suitability of a format, then please check with the course director before you submit your work. In your write-up, please clearly indicate which question/sub-question is being answered. For example, “Q5, part (b): The article omits the following crucial facts…. ”.
  • The completed assignment is to be submitted online through Moodle, as a single file, by no later than 9am on Monday, May 25th.
  1. You’ve discovered what you believe to be a cure for baldness! However, before you can market it and make millions you have to be sure that it really is effective. Propose a controlled and statistically-significant experiment that will allow you to determine whether or not the treatment is effective. Your proposal should include
  • as much detail as needed to allow a reviewer to critically assess your eventual conclusion;
  • enough detail to allow someone else to reproduce your experiment;
  • a description of what will be observed/tracked, and what outcomes are expected if the hypothesis is true. [4 Marks]

  1. The textbook makes repeated use of the phrase “We can never do just one thing”. In your own words, explain what this phrase means. (“In your own words” means that you should not just copy what the textbook says, since that could be considered plagiarism. Instead, take the core idea and express it independently, which is often called “paraphrasing”.) [2 Marks]
  2. The graph below shows the concentration of PCB contaminants measured in fish sam-ples taken from Lake Erie between 1977 and 1982. The concentration is expressed in units of milligrams (mg) of PCB per kilogram (kg) of body mass. Based only on the data in this graph answer the following questions.

Figure 1: PCB concentration measured in Walleye captured in Lake Erie. Data from DeVault, et al., J. Great Lakes Res. 22(4):884-895

  • What was the average PCB concentration in 1980? [1 Mark]
  • What were the highest and lowest likely values of the average PCB concentration in 1980? [1 Mark]
  • Qualitatively1, what was happening to the average PCB concentration in Lake Erie between 1977 and 1982? [1 Mark]
  • In what year did an average concentration of less than 1.5 mg/kg first become likely? Explain. [1 Mark]
  • Was there a statistically significant change in average PCB concentration between 1979 and 1980? Between 1980 and 1982? Explain. [2 Marks]
  • Use a simple model straight-line model based on the data available to forecast the expected PCB concentration (or a range of concentrations) in 1984. Qualitatively describe and explain your model. (You do not have to perform any calculations for this question.) [1 Mark]

4.  The graph below now shows the complete PCB concentration data set from 1977 to 1992. In light of the additional data, comment on your earlier forecast. Was it accurate? Do you think that forecast and the model that produced it were a “mistake”? Explain. [2 Marks]

Figure 2: PCB concentration measured in Walleye captured in Lake Erie. Data from DeVault, et al., J. Great Lakes Res. 22(4):884-895


  1. The following text is taken from a popular publication:

In a dramatic and controversial finding, a team of psychologists has reported that left-handed people may live an average nine years less than right-handed people. The study, which was based on an analysis of death certificates in two California counties, is the first to suggest that the well-documented susceptibility of left-handed people to a va-riety of behavioural and psychological disorders can have a substantial effect on life expectancy. Halprin and Coren based their new study on 1000 death certificates ran-domly selected from two counties in the San Bernardino area of California. In each case they contacted next of kin and asked which hand the deceased favoured. All those who did not write, draw, and throw with their right hand were classified as lefties. Someone who wrote with the right hand and threw with the left, for example, was counted as a lefty on the ground that many left-handed people were forced long ago to write with the right hand. The results shocked the researchers. The average age of death for the right-handed people in the sample was 75 years. For lefties it was 66. Among men, the average age of death was 72.3 for right-handed and 62.3 for left-handed people. “The effect was so large it is unlikely to have happened by chance,” said Halprin.

  • Carefully state the hypothesis that was tested by this specific study. [1 Mark]
  • What crucial facts and figures are missing from the report? Explain why they would be crucial for interpreting the findings? [2 Marks]
  • Given the information at your disposal, can you think of any major flaws in the design of the study? How might they be remedied? [2 Marks]
  • What conclusions can you draw about the hypothesis from this report alone? [1 Mark]
  • Consider a living apple tree as a system for which you’d like to build a conceptual model. What are the major inputs to this system? What are its major outputs? What throughputs can you describe? In particular, where do inputs of carbon (via carbon dioxide) and energy end up? [5 Marks]
  • We have seen some of the long-term consequences of the publication of fraudulent work in the health-care field – recent outbreaks of measles, among others, for example. Can you think of some practical environmental consequences that might follow from the dissemination of the work by Mangano and Sherman on Fukushima fallout? [2 Marks]