Epiville

Quizzes

Quiz 6, Module Ecological

6. What conclusions can you draw from the above scatterplots?

  1. The incidence proportion of Susser Syndrome in areas served by the Rothman and Greenland reservoirs appears to be identical
  2. Specifically, there is a negative correlation between distance from the Porks-A-Lot Farm and Susser Syndrome (as distance increases, incidence decreases)
  3. Individuals drinking Rothman Reservoir water have approximately twice the risk of developing Susser Syndrome than individuals drinking Greenland Reservoir water.
Answer (a) — incorrect: There is a clear difference in incidence proportions between the two populations
Answer (b) — correct: The line fitted to the incidence proportions of Susser Syndrome in areas served by the Rothman Reservoir suggests a strong correlation. Specifically, there is a negative correlation between increased distance from the Porks-A-Lot Farm and Susser Syndrome (as distance increases, incidence decreases).
Answer (c) — incorrect: This is an example of the 'ecological fallacy' where we are applying group-level characteristics to individuals within that group. Using the ecological study design, we can only draw conclusions concerning the groups or populations under analysis. We cannot draw conclusions about the individual members of the population because we do not have exposure and outcome data on each member.