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st: Guidance on predict in longitudinal data analyses

From   Anthony Staines <[email protected]>
To   [email protected]
Subject   st: Guidance on predict in longitudinal data analyses
Date   Fri, 09 Aug 2002 15:14:30 +0100

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 :-
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.
E-mail :- [email protected] Web :-
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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