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From |
"roland andersson" <rolandersson@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Test for trend for SIR |

Date |
Tue, 13 Nov 2007 16:48:47 +0100 |

Thanks Raoul. This works and gives almost the same result as the modelbased aproach - p=0.314 with smrby and p=0.316 with the modelbased. Roland 2007/11/13, raoul reulen <r.c.reulen@gmail.com>: > Hi Roland, > > I had the same problem with the command smrby. I changed the ado-file > and now it works. I think the problem is to do with the weights, they > need to be integer. I changed 'fweight' into 'iweight' and now it > works. > > You don't need to collapse on the incidence variable, but you do need > to calculate the expected number before you collapse the data. > > The model based option is based on a Wald test and should give you > similar results. > > Hope this helps > > Raoul > > On 13/11/2007, roland andersson <rolandersson@gmail.com> wrote: > > I have individual data with multiple records per patient after I have > > split the follow up time depending on year and age and have merged a > > variable for the incidence rate per 100.000 personyears. With the > > command > > > > xi:strate i.timeperiod,smr(inc) per (100000) > > > > I get the following result > > > > +-----------------------------------------------------------+ > > timeperiod D E SMR Lower Upper > > ----------------------------------------------------------- > > 1 7 0.43 16.102 7.677 33.777 > > 2 5 1.65 3.032 1.262 7.284 > > 3 14 2.11 6.642 3.934 11.215 > > +-----------------------------------------------------------+ > > > > I want to test for the linear trend over the timeperiods. > > > > If I try the smrby on this result I get: > > > > . smrby D E, by(timeperiod) trend > > > > Observed Expected -- Poisson Exact -- > > timeperiod D E O/E (%) [95% Conf. Interval] > > > > 1 7 0.4300 1627.9*** 655 3354 > > 2 5 1.6500 303.0 98 707 > > 3 14 2.1100 663.5*** 363 1113 > > may not use noninteger frequency weights > > r(401); > > > > Why do I get this error message? > > > > According to your second choice I use the following model on this result. > > > > glm D timeperiod, family(poisson) lnoffset(E) eform > > > > Iteration 0: log likelihood = -9.6767233 > > Iteration 1: log likelihood = -9.5071336 > > Iteration 2: log likelihood = -9.5068971 > > Iteration 3: log likelihood = -9.5068971 > > > > Generalized linear models No. of obs = 3 > > Optimization : ML Residual df = 1 > > Scale parameter = 1 > > Deviance = 7.236772128 (1/df) Deviance = 7.236772 > > Pearson = 6.884656839 (1/df) Pearson = 6.884657 > > > > Variance function: V(u) = u [Poisson] > > Link function : g(u) = ln(u) [Log] > > > > AIC = 7.671265 > > Log likelihood = -9.506897131 BIC = 6.13816 > > > > > > OIM > > D IRR Std. Err. z P>z [95% Conf. Interval] > > > > timeperiod .7561818 .2108008 -1.00 0.316 .4378616 1.305917 > > E (exposure) > > > > ie there is no linear trend p=0.316 > > > > Is this a correct use of the glm model? Or can I use some other method > > on the original dataset? If I collapse the dataset what happens with > > the incidensvariable which should not be aggregated but stay the same. > > Or do I have to collapse the dataset and merge the incidensvariable > > after the collapse? > > > > Roland Andersson > > > > > > 2007/10/18, raoul reulen <r.c.reulen@gmail.com>: > > > Hi > > > > > > I'm not exactly sure what you want to do, but the title of the message > > > suggests you want to do a test for linear trend accros several SIRs. > > > What I normally do is use smrby.ado because it includes a test for > > > trend and heterogeneity. Alternatively, you might want to model the > > > SIRs by using a GLM model with a Poisson error structure and then fit > > > the factor of interest as a consecutive non-negative integer variable. > > > Make sure you collapse your data before you model it. > > > > > > .collapse (sum) _d E pyrs, by(timeperiod) > > > .xi, noomit:glm _d i.timeperiod if E!=0,fam(pois) lnoffset(E) eform noconstant > > > > > > gives you the SIRs > > > > > > .xi, noomit:glm _d timeperiod if E!=0,fam(pois) lnoffset(E) eform noconstant > > > > > > gives you the p-value for linear trend > > > > > > _d is the numner of events, E the number of expected. The p-value for > > > timeperiod should give you the test for linear trend accross the > > > groups. > > > > > > > > > Hope it helps > > > > > > Raoul Reulen > > > Cancer Research UK Graduate Training Fellow > > > > > > > > > > > > > > > > > > On 17/10/2007, roland andersson <rolandersson@gmail.com> wrote: > > > > I have used strate.ado to calculate standardised incidence ratios with > > > > standardisation for age, sex and timepriod. I want to make inferences > > > > on the development of the SIRs over three timeperiods. Can you help me > > > > with instruction how to do this? > > > > * > > > > * 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/ > > > > > > > > > > > > > -- > > > ------------------------------------------------------- > > > Raoul C. Reulen > > > Cancer Research UK Training Fellow > > > * > > > * 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/ > > > > > -- > ------------------------------------------------------- > Raoul C. Reulen > Cancer Research UK Training Fellow > * > * 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**:**Re: st: Test for trend for SIR***From:*"roland andersson" <rolandersson@gmail.com>

**Re: st: Test for trend for SIR***From:*"raoul reulen" <r.c.reulen@gmail.com>

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