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From |
Leonelo Bautista <lebautista@wisc.edu> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: RE: metan command & binary variables |

Date |
Wed, 21 Apr 2004 07:45:29 -0500 |

Odds ratios and relative risks are calculated different. (4/5)/(4/51)=10.2 this is the ratio of two odds (4/(5+4))/(4/(51+4))=6.1 this is the ratio of two probabilities (risks) Leonelo E. Bautista, University of Wisconsin Population Health Sciences -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of cthompson@dfpm.utah.edu Sent: Tuesday, April 20, 2004 5:22 PM To: statalist@hsphsun2.harvard.edu Subject: st: metan command & binary variables Hello All -- I'm using Stata version 8.2 and I hope someone can clarify a question I have regarding the -metan- command and it's estimation of odds ratios versus risk ratios. Suppose I have two rates that capture success on a diet where the first rate represents those who adhered to a certain protocol and the second rate represents those who dropped from the protocol after follow-up. Each rate is captured by the number successful divided by the number in the respective group (adhere vs follow-up). I created four variables: num1, den1, num2, & den2 where num1 is the # of successful dieters that adhered & den1 is the # of adherers; a similar interpretation follows for num2 & den2. When I run the following code -metan num1 den1 num2 den2, random or label(namevar=Trial)- I get an 'odds ratio' that works out to equal the ratio of the rate from the adherers over the rate for the droppers. If I specify -rr- instead of -or- the results differ and I am at a loss as to why. Consider the following values: num1=4, den1=5, num2=4, den2=51 where the calculation of (4/5)/(4/51) = 10.2, which is consistent with -metan..., or- but if I specify -metan..., rr- I get a 'risk ratio' of 6.111. Am I not understanding the vernacular or can someone clue me into how the 6.111 was calculated? As always, your input is much appreciated! thank you -- Clint Thompson * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: metan command & binary variables***From:*<cthompson@dfpm.utah.edu>

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