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DiegoGil
‎09-01-2015
  • 3 Posts
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Re: Covariate slopes in Proc Mixed: an interaction problem

by Calcite | Level 5 in Statistical Procedures
‎07-02-2013 09:16 AM
‎07-02-2013 09:16 AM
Spot on Steve! Thanks a lot! One final thing, I assumed that one should never put terms in an interaction that have not appear on their own in the model, so I guess this method you gave me is not good for fixed effects, just for estimates of interactions, is this right? Best wishes Diego ___________________________________________________________________ Diego Gil   Departamento de Ecología Evolutiva   Museo Nacional de Ciencias Naturales (CSIC)   José Gutiérrez Abascal, 2   28006 Madrid   Spain   Tel: 00 34 91 411 13 28, ext. 1141   Fax: 00 34 91 564 50 78   web site: www.behavecol.es ... View more

Re: Covariate slopes in Proc Mixed: an interaction problem

by Calcite | Level 5 in Statistical Procedures
‎07-02-2013 04:36 AM
‎07-02-2013 04:36 AM
Dear Steve, Thanks for your mail. You were right about the model, it's a bit more complex but I reduced it for this particular problem. So, then if we use /solution we obtain the following ("puesta" is group; and "t014" is temperature): You said that the slope for group 2 is actually that of temperature, thus: -1.85; while that of the first group would be then (group 2 minus group 1) = 0.2, is this correct? Then, for the SE, if I use noint I get this, but there is no different SE for the slopes as you said, what am I doing wrong? Thanks a lot for your help, this is most useful!! Diego ... View more

Covariate slopes in Proc Mixed: an interaction problem

by Calcite | Level 5 in Statistical Procedures
‎06-28-2013 02:52 AM
‎06-28-2013 02:52 AM
Hi there, I'm out of my depth here and I wonder if someone has a solution. I have this analysis in which I test the effect of temperature in nestling growth. I have several chicks per nest, thus the nest is a random factor and I run this in Proc Mixed. The effect of temperature is different for two treatment groups, and this is reflected in a significant interaction of temperature*group. Fine, so the two slopes are different frome each other. Cool, this is expected. The problem is that I need to know whether these two slopes are significantly different from 0 (in the graph it looks as if one of them is negative, but the other one could be positive or simply not different from 0). My referees want to know that (and so do I!). The SAS estimate shows that one of the slopes is set to 0 by default, so I only have an estimate for the other slope. How can I obtain the two "real" slope estimates? If I split the dataset in two, and I calculate the slopes separately, the effect disappears, so this is not good. Any ideas?? Thanks millions! Best wishes Diego Gil ... View more
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