Hi all,
I am using the lme function to run a random coefficient model. Please see
output (mod1) as below.
I need to obtain the pvalue for the fixed effect. As you can see,
the pvalues given using the summary function is different from the
resutls given in anova function.
Why should they be different and which one is the correct one to use?
Thanks!
Hanna
> summary(mod1)
Linear mixed-effects model fit by REML
Data: minus20C1
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) typ 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
> anova(mod1)
numDF denDF F-value p-value
(Intercept) 1 31 2084.0265 <.0001
type 1 4 10.8957 0.0299
months 1 31 38.3462 <.0001
type:months 1 31 5.4118 0.0267
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