[R] Confidence interval for the mean in the random intercept and random slople model

[li li]

Hi all,
  I am fitting a random slope and random intercept model usign lme
fucntion as shown below. Type is factor with two levels. I would like
to to find a confidence interval for mean of this model. Note that the
variance we use in finding the confidence interval should include the
variariance component from random effect.  Any suggestions?


## using lme function
> mod_lme <- lme(ti  ~ type*months, random=~ 1+months|lot, na.action=na.omit,
+ data=one, control = lmeControl(opt = "optim"))
> summary(mod_lme)
Linear mixed-effects model fit by REML
 Data: one
        AIC       BIC   logLik
  -82.60042 -70.15763 49.30021

Random effects:
 Formula: ~1 + months | lot
 Structure: General positive-definite, Log-Cholesky parametrization
            StdDev       Corr
(Intercept) 8.907584e-03 (Intr)
months      6.039781e-05 -0.096
Residual    4.471243e-02

Fixed effects: ti ~ type * months
                     Value   Std.Error DF   t-value p-value
(Intercept)     0.25831245 0.016891587 31 15.292373  0.0000
type            0.13502089 0.026676101  4  5.061493  0.0072
months          0.00804790 0.001218941 31  6.602368  0.0000
type:months -0.00693679 0.002981859 31 -2.326329  0.0267
 Correlation:
               (Intr) typPPQ months
type           -0.633
months         -0.785  0.497
type:months  0.321 -0.762 -0.409

Standardized Within-Group Residuals:
          Min            Q1           Med            Q3           Max
-2.162856e+00 -1.962972e-01 -2.771184e-05  3.749035e-01  2.088392e+00

Number of Observations: 39
Number of Groups: 6