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From |
"Carlo Lazzaro" <carlo.lazzaro@tiscalinet.it> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: R: What does -koopmani- output? odds ratios or risk ratios? |

Date |
Fri, 13 Mar 2009 20:01:50 +0100 |

Dear Tiago, I actually do not know the features of -koopmani-. However, sticking to basic epidemiological formulae, I would agree with you. In fact, apart from 95% CI, the point estimate of OR should be 36, whereas the point estimate of RR (as you state), turns out to be 4.5. However, as reported in the following article (please, find the reference below), there's sometimes some "straddling" between OR and RR. Hence, it may be that, in your example, the OR is in fact the ratio (.9/.2=4.5) between the estimate of the probability of having the event in Group 1 (ie 36/40=.9) and in Group 2 (ie 16/80=.2), respectively Jun Zhang; Kai F. Yu Odds Ratio in Cohort Studies of Common Outcomes What's the Relative Risk?: A Method of Correcting the http://jama.ama-assn.org/cgi/content/full/280/19/1690 Sorry I cannot give you a more helpful hint. Kind Regards and enjoy your W_E, Carlo -----Messaggio originale----- Da: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] Per conto di Tiago V. Pereira Inviato: venerdì 13 marzo 2009 16.57 A: statalist@hsphsun2.harvard.edu Oggetto: st: What does -koopmani- output? odds ratios or risk ratios? Dear statalisters, Working with -koopmani-, one types: . koopmani 36 40 16 80 and gets: | Event | Proportion | Yes No | Total Yes -----------------+------------------------+---------------------- Group1 | 36 4 | 40 0.9000 Group2 | 16 64 | 80 0.2000 -----------------+------------------------+---------------------- Total | 52 68 | 120 0.4333 | | | Point estimate | [95% Conf. Interval] -----------------|------------------------+---------------------- Odds Ratio | 4.5 | 2.939633 7.152252 ----------------------------------------------------------------- That estimate of 4.5 is actually the risk ratio, isn´t it? Or am I doing a big confusion? . cci 36 4 16 64 All the best, Tiago * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**st: Cox reg sample size formula in our book***From:*Enzo Coviello <enzo.coviello@tin.it>

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