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st: Guidance on predict in longitudinal data analyses


From   Anthony Staines <anthony.staines@ucd.ie>
To   statalist@hsphsun2.harvard.edu
Subject   st: Guidance on predict in longitudinal data analyses
Date   Fri, 09 Aug 2002 15:14:30 +0100

Hi,
I have two questions - one is a Stata question, the second is a more general statistical question.

I am working on a clinical trial of exercise in pregnancy, where a mjor interest is in describing the temporal changes in physiological variable measured during and after pregnancy.

I want to summarise the results of some models by presenting the modelled values of physiological variables at 6 weeks and 36 weks of gestation like this :-
pontoon
Variable 6 weeks 36 weeks
PEFR 500 450
V0 2.3 1.9
GET 0.75 0.4
etc.. (The numbers are invented).

Stata question
How can I use 'predict' to generate values (and confidence intervals) for model predictions at specifc values of the time variable?
I don't want to generate a datset with the mean values of the predictor variables at every timepoint, unless I have to.

More general question.
For these particular data random variable models didn't fit any better than simpler models - but it made me think, and I have no idea what a 'prediction' for a random variables model means - does it include some estimate of the 'mean' values of the random variable? Any guidance?

Best wishes,
Anthony Staines
--
Anthony Staines, Lecturer in Epidemiology, Department of Public Health,
UCD, Earlsfort Terrace, Dublin2, Ireland. http://phm.ucd.ie/
E-mail :- Anthony.Staines@ucd.ie Web :- http://astaines.ucd.ie/
Work :- + 353 1 716 7345 Fax :- +353 1 716 7407
Home :- + 353 1 849 1089 Mobile :- +353 1 86 606 9713


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