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From |
Richard Williams <richardwilliams.ndu@gmail.com> |

To |
statalist@hsphsun2.harvard.edu, statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Logistic growth curve question |

Date |
Sun, 13 Apr 2014 18:55:07 -0500 |

1. Is the Stata dataset easily available somewhere?

At 04:07 PM 4/13/2014, Dave Garson wrote:

For instructional purposes, I am trying to replicate the classicPothoff & Roy linear growth model in SPSS, SAS, and Stata.While there are variations on this model, the version I amreplicating has the following attributes and constraints:1. y1 through y4 are distance measurements at ages 8, 10, 12, and 142. ICEPT is the intercept latent variable, whose slopes areconstrained to 1.0. It is modeled as a cause of y1 through y4.3. SLOPE is the slope latent variable, whose paths are constrainedto 8, 10, 12, and 14. It is also modeled as a cause of y1 through y4.4. Error variances are constrained equal. 5. Dependent means are constrained to 0.I get the same results in SAS and SPSS but very differentcoefficients in Stata, with which I am less familiar. The estatframework postestimation command in Stata shows the five modelaspects above are met, but coefficients differ a great deal.Below is my SAS code and my Stata code. My question is, what needsto be changed in the Stata code to give results consistent withSPSS, SAS, and the model described above?SAS SYNTAX: PROC CALIS DATA=in.royfm MODIFICATION EFFPART PLATCOV;/* Above, MODIFICATION requests Lagrange multipliermodification indices *//* Above, EFFPART requests a partition of total effects *//* Above, PLATCOV requests latent variable covariances andscore coefficients */PATH /* Below, there are four time periods, y1 - y4 */ y1 y2 y3 y4 <--- ICEPT = 1.0 1.0 1.0 1.0, y1 y2 y3 y4 <--- SLOPE = 8.0 10.0 12.0 14.0;/*Above, intercept paths constrained to 1, slopes arecostrained to linear growth */PVAR y1 = variance1, y2 = variance1, y3 = variance1, y4 = variance1, ICEPT = ivariance, SLOPE = svariance; /* Above, time variables are constrained to have equal error variance *//* Above, variances of ICEPT and SLOPE are freely estimatedas ivariance and svariance */PCOV ICEPT SLOPE = cov1; /* Above, ICEPT and SLOPE covariance is freely estimated as cov1 */ MEAN y1 = 0, y2 = 0, y3 = 0, y4 = 0, ICEPT = imean, SLOPE = smean; /* Above, time variables constrained to a mean of 0 *//* Above, means of ICEPT and SLOPE are freely estimated asimean and smean */RUN; STATA SYNTAX sem (ICEPT -> y1@1 y2@1 y3@1 y4@1) (SLOPE -> y1@8 y2@10 y3@12 y4@14), latent(ICEPT SLOPE) cov( e.y1@variance1 e.y2@variance1 e.y3@variance1 e.y4@variance1 SLOPE*ICEPT) means(ICEPT SLOPE) noconstant Advice appreciated on list or to david_garson@ncsu.edu Best to all, Dave * * 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/

------------------------------------------- Richard Williams, Notre Dame Dept of Sociology OFFICE: (574)631-6668, (574)631-6463 HOME: (574)289-5227 EMAIL: Richard.A.Williams.5@ND.Edu WWW: http://www.nd.edu/~rwilliam * * 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: Logistic growth curve question***From:*Dave Garson <garson@ncsu.edu>

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