[R-sig-ME] Basic question about interpretation of lme () result.

[R.S. Cotter]

DeaR mixed effect model users

I'm need some advice regarding interpretation of the lme () result. My
question is possible too basic, but I hope someone could help me with
advices (it may be valuable for other lme() new beginners).

Respons: Speed
Fixed effects: Fuel, CarMod (1,2&3), Driver (Old or Young), and Fuel*CarMod.
Random effects: Place

Questions regarding my model, se below:

1. Is it right to interpret that CarMod2 is significant different from CarMod1?
2. Is it right to interpret that the effect of Fuel is different in
CarMod2 compared to CarMod1?
3. Is there a guideline for reporting lme() result? I'm uncertain
whether to report this result as a table with only the estimates from
the lme () or a table with only the anova (mod1)?


> mod1 <- lme(Speed ~ Fuel + Car + Driver + Fuel*Car, random=~1|Place,data=test)
> summary(mod1)
Linear mixed-effects model fit by REML
 Data: test
       AIC      BIC    logLik
  261.2013 275.6996 -121.6007

Random effects:
 Formula: ~1 | Place
            (Intercept)         Residual
StdDev: 0.0003238738   5.013858

Fixed effects: Speed ~ Fuel + Car + Driver + Fuel * Car
                       Value        Std.Error     DF   t-value       p-value
(Intercept)        -29.33479  12.743084   30   -2.302017   0.0285
Fuel                10.04684    1.408789    30    7.131542   0.0000
CarMod2         46.55593    14.192029   7     3.280428   0.0135
CarMod3          1.65157     18.247158   7     0.090511   0.9304
DriverYoung     26.65219    1.688643    30   15.783202  0.0000
Fuel:CarMod2  -5.53264     1.624159    30   -3.406464   0.0019
Fuel:CarMod3  -0.18452      2.010470   30   -0.091779   0.9275

Number of Observations: 44
Number of Groups: 10
> anova(mod1)
               numDF   denDF    F-value     p-value
(Intercept)     1        30        8487.520  <.0001
Fuel             1        30         340.661   <.0001
Car              2         7            6.283     0.0274
Driver           1        30         235.860    <.0001
Fuel:Car       2        30           8.655      0.0011

Best regards R.S. Cotter