[R-sig-ME] Wrong degrees of freedom in lmer model?

Ryan Hope rmh3093 at gmail.com
Thu Apr 2 21:51:49 CEST 2009

I am trying to use the lmer function to analyze the data from the
thesis experiment. The response variable is a continuous variable,
completion time. I have 2 fixed factors, number of targets (4-levels:
4,9,14,19) and displacement per second (DPS) (3-levels: 72.42, 84.99,
88.99). I also have 3 random variables, participants, block (which
group the replicates of a combination of fixed factors), and target
displacement. The R code that I am using is listed below:


Im not even sure if the lmer model I am using is 100% correct but it
seems the best to based on what I've read on
Anyway, I do not understand the degrees of freedom reported by the
anova function based on my model (shown below):

Analysis of Variance Table
        Df Sum Sq Mean Sq    F value
Targets  4  33393    8348 39411.3500
DPS      1      2       2     7.7816

Since there are 4 levels of the Target factor, shouldn't the Df for
Targets be 3 not 4?


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