[R-sig-ME] (stupid) results interpretation question
CL Pressland
Kate.Pressland at bristol.ac.uk
Tue Jun 9 13:29:36 CEST 2009
I have a seemingly stupid but fundamental question I need answering.
I've had some strange plots and am now seriously questioning my
interpretation of the lmer output: if I have a fixed effects results table
that looks like this, can someone please check I'm interpreting it
correctly?
---------
Fixed effects:
Estimate Std. Error t value
1 (Intercept) -1.58481 0.18585 -8.53
2 GM1 0.02400 0.20472 0.12
3 GM2 0.17941 0.15916 1.13
4 Morph1 -1.54068 0.02202 -69.97
5 GM1:Morph1 -0.21681 0.04701 -4.61
6 GM2:Morph1 -0.12910 0.03321 -3.89
---------
1. Intercept is GM0 and Morph0
In my understanding the estimates given are the differences from the
intercept alone so would give mean values for each category of:
1 -1.58481
2 -1.5601
3 -1.4054
4 -3.12549
5 -1.80162
6 -1.71391
Is this correct? Have I made a mistake in just looking at the difference
from the intercept or do 2,3 and 4 need to be taken into account when
calculating 5 and 6 i.e. 6 = 1 + 3 + 4?
I don't want to plough through thinking I've understood this when I may not
have! I've tried looking in Pinheiro and Bates etc but they all just say
the "estimate is the difference in the means" - I want to make sure I'm
interpreting it correctly.
Anyone who can spare this simpleton student a swift reply would really help
me out.
----------------------
Kate Pressland
School of Biological Sciences
University of Bristol
Woodland Road
Bristol, BS8 1UG
Kate.Pressland at bristol.ac.uk
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