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From |
"Tiago V. Pereira" <tiago.pereira@incor.usp.br> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
RE: st: Other definition of -tabodds-? |

Date |
Fri, 15 Aug 2008 09:35:11 -0300 (BRT) |

Herve, I believe there is no routine already implemented to run exactly the analysis you are looking for. However, the main point in your analysis is to obtain a reliable estimate of the standard error of that ratio. If you can accomplish this task, you can apply tests for trend and homogeneity as you just did with -tabodds- using simple do files. If you need further help, please, do not hesitate to contact me through private messages. Cheers! Tiago --------------------------------------------------------- Herve wrote: Dear Statalisters: I use -tabodds- to compute two ratios (cases/controls) (20/13 and 22/11 in the example below) and test the evolution of these ratios (see the output below). tabodds small_profit post_ifrs if country=="AUS" & sample_sum==1 -------------------------------------------------------------------------- post_ifrs | cases controls odds [95% Conf. Interval] ------------+------------------------------------------------------------- 0 | 20 13 1.53846 0.76531 3.09270 1 | 22 11 2.00000 0.96985 4.12436 -------------------------------------------------------------------------- Test of homogeneity (equal odds): chi2(1) = 0.26 Pr>chi2 = 0.6115 Score test for trend of odds: chi2(1) = 0.26 Pr>chi2 = 0.6115 I would like to define the ratios in a different way: Instead of cases/controls, I would like to have: (cases-controls)/(cases+controls). With the -matrix- command and scalars, I manage to get the ratios: count if post_ifrs==0 & small_profit==1 & country=="AUS" & sample_sum==1 scalar N1 = r(N) count if post_ifrs==0 & small_profit==0 & country=="AUS" & sample_sum==1 scalar N2 = r(N) scalar odds=(N1-N2)/(N1+N2) matrix m1 = N1, N2, odds matrix rownames m1 = "Pre IFRS" count if post_ifrs==1 & small_profit==1 & country=="AUS" & sample_sum==1 scalar N3 = r(N) count if post_ifrs==1 & small_profit==0 & country=="AUS" & sample_sum==1 scalar N4 = r(N) scalar odds2=(N3-N4)/(N3+N4) matrix m2 = N3, N4, odds2 matrix rownames m2 = "Post IFRS" matrix m3 = m1\m2 matrix colnames m3 = "Cases (Small profit)" "Controls (Small loss)" Odds matrix list m3 Here is the output: m3[2,3] Cases (Small profit) Controls (Small loss) Odds Pre IFRS 20 13 .21212121 Post IFRS 22 11 .33333333 I would like to know if there is an equivalent command to -tabodds- or a specific way to test the evolution of the two ratios: (N1-N2)/(N1+N2) (N3-N4)/(N3+N4) respectively 0.2121 and 0.3333 in my example. Best regards Herve Stolowy * * 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/

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