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From |
nicola.baldini2@unibo.it |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: how to use ztnb? |

Date |
Fri, 22 Feb 2008 18:57:29 +0100 |

Which is the question, here? Your knowledge of -ztnb- seems to exceed mine. Your code xi:ztnb mf-counts i.age [fweight = freq] if mf-counts>0, dispersion(mean) let you estimate a zero truncated NB mobel where the dispersion (the parameter called dispersion in Stata) is a nonlinear (exponential) function of the mean. As a default, it includes a test about the hypothesis that the dispersion is a nonlinear (exponential) function of the mean vs. the dispersion is a constant (if the test is insignificant, then the dispersion is a constant). Nicola At 02.33 19/02/2008 -0500, Subramanian Swaminathan wrote: >Dear stata listers, > >I am trying to fit a zero-truncated negative binomial >model to my count >data. The data variables are mf-counts, age, >frequency. The model that I >would like to fit is of the form: >xi:ztnb mf-counts i.age [fweight = freq] if >mf-counts>0, dispersion(mean) > >Kindly note that my dispersion parameter is not a >constant but is a >non-linear function as given below: > >k = k0+beta*mean**gamma (0<gamma < infinity) > >where, >'k' is the dispersion parameter 'k' ( in stata, k=log >(1/alpha) of the >negative bonomial model > >beta & gamma = coefficients to be estimated > >In this model I want to test the hypothesis that >beta=0 against beta not >equal to 0. > >could anyone help me out, how the stata code should be >written to estimate >the parameters of the model? > >kindly note that i am new 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/

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