By default, qdec uses "DODS" - different offset, different slope. This
means that each class gets its own offset (as with DOSS), but it also
gets its own slope, so 0 0 +1 -1 will test the difference between
slopes., and 0 0 +1 +1 will test for the slope averaged across the
classes. With DOSS, there is only one slope for each continuous variable
regardless of the number of classes, and 0 0 1 will test it. I don't
think that +1 -1 +1 tests anything meaningful.
doug
Cameron Ellis wrote:
Hi,
I have been running analyses in qdec and glmfit and comparing the
results.
I am puzzled by the results of one analysis that compares two groups.
When
I loaded a table.dat file in qdec and selected the variables of interest,
an fsgd file containing only those variables was generated in the
analysis, no problem so far. The problem is that the contrast.mat file
contains more "identifiers" than variables I selected.
The generated fsgd file looks something like this:
Class a
Class b
Variables x
Input subj1 a 1
Input subj2 b 4
Input subj3 a 2
Input subj4 b 1
and the generated contrast.mat file looks like this:
0 0 +1 -1
I thought that to generate a contrast for these two groups of the
correlations between thickness and variable x I shouldn't the
contrast.mat
file that looks like this:
+1 -1 1
Thanks for any insight,
Cameron
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