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EPID 766: Analysis of Longitudinal Data from ... - NCSU Statistics

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CHAPTER 1 Epid <strong>766</strong>, D. Zhang<br />

estimates the following quantity<br />

θ =<br />

P[E|D]/(1 − P[E|D])<br />

P[E|D]/(1 − P[E|D])<br />

= P[D|E]/(1 − P[D|E])<br />

P[D|E]/(1 − P[D|E]) .<br />

• If disease is rare, i.e., P[D|E] ≈ 0, P[D|E] ≈ 0, relative risk <strong>of</strong><br />

disease can be approximately obtained:<br />

θ ≈ P[D|E]<br />

P[D|E]<br />

= relative risk.<br />

More efficient than prospective cohort study in this case.<br />

• Problem: recall bias! (it is difficult to ascertain exposure<br />

history E.)<br />

Graduate Summer Session in Epidemiology Slide 10

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