R help - Dec 2004 - How to test the significance of a value estimated with lme?

Hi,

After running an experiment in economics involving 3 treatment variables
(Complete, High and Ksup), 32 Groups of subject (4 groups for each of the 8
treatment combinations) and 12 Periods, I've estimated the following model
in which all coefficients are significant:

y <-
lme(Diff~factor(Complete)+factor(High)+factor(Ksup)+Period+factor(High):Period+factor(Ksup):Period,
random=~1 | Group, method='ML').

The result is:

      (Intercept) -10.99 
      factor(Complete)1 -9.05 
      factor(High)1 -12.28 
      factor(Ksup)1 14.69 
      Period 1.12 
      factor(High)1:Period 0.98 
      factor(Ksup)1:Period -0.85 


This allows me, if I'm not wrong, to estimate for example the value of the
dependent variable Diff in period 5 under the High and Complete (but not the
Ksup) conditions as: -10.99 - 9.05 - 12.28 + 1.12*5  + 0.98*5.

Now, I'd like to test whether this estimated value is significantly
different from 0: How should I do?

Thanks a lot!

Francois Cochard
University of Toulouse 1, France.



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