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From |
Lucas <lucaselastic@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Clarification Re: Stata 13, + |

Date |
Tue, 11 Jun 2013 07:27:23 -0700 |

Thanks for the clarifications. I look forward to 1)ordering stata 13 sometime this week and 2)using the new materials that may be developed on the multilevel commands. Thanks again! On Mon, Jun 10, 2013 at 3:21 PM, Rafal Raciborski, StataCorp <rraciborski@stata.com> wrote: > Sam <lucaselastic@gmail.com> has a question about Stata licensing: > >> Am I correct in understanding that the perpetual license entails >> exactly the same terms as before if I do not choose the maintenance >> option? Am I correct in understanding that I will be able to update >> stata (as long as it is still stata 13.x) if I choose not to pay the >> maintenance option? Or, am I mistaken, and the maintenance fee is >> required to "maintain" an up-to-date stata prior to the next major >> release? > > Your understanding is correct. A perpetual Stata license still works > exactly > as it always has, including free updates via the -update- command along > the > way, whether you have maintenance or not. If you have maintenance in > effect > and another major version of Stata comes out (i.e. Stata 14), you > automatically > receive a new perpetual license to that major version. > > Sam also asked about multilevel mixed-effects models where level-2 > variables > are introduced for level-1 slopes: > >> It is great that stata allows users to look through the manual for the >> new release early. I did, and found myself wishing for one simple >> change in the multilevel segment, an addition, really. Many analysts >> use the multilevel model to introduce level-2 variables into equations >> for level-1 slopes. So, for example, the analyst might add a variable >> for per pupil expenditure to the model such that it alters the slope >> for parents' income in a model predicting student test score. > > To fit such models in Stata, one needs to translate the multistage > formulation > of a mixed-effects model into a one-equation formulation specified for the > outcome. For example, consider a two-stage formulation: > > y_ij = eta_i0 + eta_i1*x_ij + e_ij (level 1) > eta_i0 = b_00 + b_01*z0_i + u_i0 (level-2 intercept) > eta_i1 = b_10 + b_11*z0_i + u_i1 (level-2 slope) > > which contains one level-1 variable x and one level-2 variable z0, > which varies at the slope and intercept levels. > > To obtain a one-equation formulation, we substitute eta_i0 and eta_i1 into > the level-1 equation: > > y_ij = (b_00+b_01*z0_i+u_i0) + (b_10+b_11*z0_i+u_i1)*x_ij + e_ij > (after rearranging terms) > = (b_00 + b_01*z0_i + b_10*x_ij + b_11*z0_i*x_ij) <-- fixed > + (u_i0 + x_ij*u_i1 + e_ij <-- random > > To fit this model using, for example, -mixed-, we would type > > . mixed y x z0 c.x#c.z0 || id: x > > where 'id' is the level-2 identifier, y is the outcome variable, and x and > z0 > are the corresponding level-1 and level-2 variables. We assumed that x > and z0 > are continuous and used the factor notation to include their interaction > in > the model. > > We will consider including an example of a multistage formulation in our > documentation. For more examples, Sam may also look at Rabe-Hesketh & > Skrondal (2012), for example, chapters 4.9 and 7.4. > > --Rafal > rraciborski@stata.com > > References > > S. Rabe-Hesketh & A. Skrondal. 2012. Multilevel and Longitudinal Modeling > using Stata. Stata Press, 3rd edition. > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/faqs/resources/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/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Clarification Re: Stata 13, +***From:*rraciborski@stata.com (Rafal Raciborski, StataCorp)

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