I am using lme from the nlme package to fit a mixed model. We have
observations nested in patients(encounters) and patients nested in groups (2
different treatments). We are interested in the differences between the 2
groups, both the means and the standard deviations (are patients in group A
less variable than those in group B? both within patient and between patient
within group).
Here is the call from my lme object:
> fit3$call
lme.formula(fixed = BG ~ group, data = bg, random = list(Encounter =
pdDiag(~group -
1)), weights = varIdent(form = ~1 | group))
then I call the intervals function:
Approximate 95% confidence intervals
Fixed effects:
lower est. upper
(Intercept) 123.40005 126.88445 130.36885
groupB 17.44991 23.60049 29.75107
attr(,"label")
[1] "Fixed effects:"
Random Effects:
Level: Encounter
lower est. upper
sd(groupA) 16.62769 19.13351 22.01698
sd(groupB) 24.01774 27.63703 31.80171
Variance function:
lower est. upper
A 0.8270135 0.8534733 0.8807797
attr(,"label")
[1] "Variance function:"
Within-group standard error:
lower est. upper
33.56082 34.29237 35.03987
and this gives me most of what I want, the only exception is that I (actully my
client) want the interval for the Within-group standard error of group A (the
last interval shows it for group B and the Variance function shows the interval
for their ratio).
Any suggestions?
Thanks,
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