The graph doesn’t show us that cigarette smoking is known to be a direct cause of Lung Cancer. We have that info from another source already. We can use the information in this graph, plus our knowledge about the association of smoking with Lung Cancer, to perform deductive reasoning to make a guess about what is going on. We can form a hypothesis, and then use Analytical reasoning in Section 7 to test out hypothesis,
2. Compare the two curves for male vs. female, can you deduce the reason why the two curves are not directly on top of each other?
3. Why does the male curve show a higher death rate?
4. Why does the male curve shoot up earlier in the 20th century than does the female curve?
5. A hypothesis is a testable statement. What hypothesis could you draw from your reasoning?
Section 7 – Analytical Epidemiology
Re-read this section and answer the questions that follow:
As noted earlier, descriptive epidemiology can identify patterns among cases and in populations by time, place and person. From these observations, epidemiologists develop hypotheses about the causes of these patterns and about the factors that increase risk of disease. In other words, epidemiologists can use descriptive epidemiology to generate hypotheses, but only rarely to test those hypotheses. For that, epidemiologists must turn to analytic epidemiology.
The key feature of analytic epidemiology is a comparison group. Questions:
6. Re-read the statement from the reading above: “The key feature of analytic epidemiology is a comparison group.”
What is a comparison group and how does it work?
7-8. Using your hypothesis that you developed in question 5 above, suggest an Analytical study that would allow you to test your hypothesis.
7. Consider the rationale of setting up an Experimental Study. One possible way to do this would be to set up groups of male and female teenagers, teach half them to smoke, get them to commit to smoking for the rest of their lives. Set up a comparison group, get them to commit to not smoking for the rest of their lives. Follow them for the next 25-40 years to chart how many of them die of Lung Cancer every year.
Would this be the most ethical way to test your hypothesis? Answer yes or no, and explain your answer.
8. Instead, consider the setting up an Observational Study. read about and consider the three types of studies: Cohort, Case-control and Crossectional Studies.
Choose one of these three approaches, and briefly describe how you would do it. Be sure to say what your comparison group would be.
Sections 8, 9 and 10. Read these sections and think about these concepts relate to the HIV epidemic.
Now read Section 1.10. Work through the problem in Exercise 1.9, as it applies to Dengue Fever. Check your answers on the link to be sure that you understand how these concepts work.
Challenge: After reading this information to find out what each of these terms mean, now outline the chain of infection for HIV by identifying the reservoir(s), portal(s) of exit, mode(s) of transmission, portal(s) of entry, and factors in host susceptibility for HIV.
1. Reservoirs:
2. Portals of exit:
3. Modes of transmission:
4. Portals of entry:
5. Factors in host susceptibility:
