1. Understanding Observational Studies Lecture 11 Section 3.4 Mon, Feb 5, 2007

2. Types of Observational Studies Retrospective study Prospective study

3. Example Which studies were prospective? Which were retrospective?  Empathy study.  Migraine study.

4. Example Example 3.7, p. 160 – High-fiber Diet Cuts Heart-attack Risk in Men.

5. As a Prospective Study As a prospective study. 1800 16200 Low-fiber diet 1600 23400 High-fiber diet Heart attack No heart attack Population #1 p 1 = 10% Population #2 p 2 = 6.4%

6. Example Describe the design of this study had it been set up as a retrospective study.

7. Example As a retrospective study. 18001600 1620023400 Low-fiber diet High-fiber diet Heart attack No heart attack Population #1 p 1 = 47% Population #2 p 2 = 59%

8. Prospective Studies In a prospective study, the explanatory variable’s value is often its present value (but not always). How would the researchers determine the values of the response variables?

9. Retrospective Studies In a retrospective study, the response variable’s value is again often its present value (but not always). How would the researchers determine the values of the explanatory variables?

10. Difficulties in Observational Studies In an observational study,  The researchers cannot control the explanatory variables.  The researchers cannot control the confounding variables. In the example about fiber vs. heart-attack risk, what are some plausible confounding factors?

11. BAD Monograms Monogrammic Determinism Do Bad Monograms Spell R.I.P.?