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Understanding Observational Studies

Understanding Observational Studies. Lecture 11 Section 3.4 Mon, Feb 5, 2007. Types of Observational Studies. Retrospective study Prospective study. Example. Which studies were prospective? Which were retrospective? Empathy study. Migraine study. Example.

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Understanding Observational Studies

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  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. High-fiber diet 1600 23400 Population #2 p2 = 6.4% Population #1 p1 = 10% As a Prospective Study • As a prospective study. Low-fiber diet 1800 Heart attack 16200 No heart attack

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

  7. Example • As a retrospective study. Low-fiber diet High-fiber diet 1800 1600 Heart attack Population #1 p1 = 47% 16200 23400 No heart attack Population #2 p2 = 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.?

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