Hi, related question-if you want to test the average slope/effect don't you need to weight each variable by 1/(# of variables)? I thought if you weight each column of interest by 1 you're effectively summing the beta for each? Then And test the average effect against the baseline, if your baseline is explicit you'd weight that by -1, but if your baseline's implicit you wouldn't have any negative values?
Thanks for the clarification!
On 29/01/2010, at 10:12, "MCLAREN, Donald" <[log in to unmask]<mailto:[log in to unmask]>> wrote:
Assuming that these are both continuous variables, it means that the slope of the relationship between X1 and Y is greater than the relationship between X2 and Y. X1 has 1 over it and X2 has a -1 over it. You can only tell +/- correlation if you have a 1 or -1 over a single column OR if you want the average slope you can have 1s or -1s over several columns, but you can have both. As soon as you have both, then you are testing the difference in the slopes.
Best Regards, Donald McLaren
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D.G. McLaren
University of Wisconsin - Madison
Neuroscience Training Program
Office: (608) 520-0586
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On Fri, Jan 29, 2010 at 3:03 AM, Kelly Atalaia Silva <<mailto:[log in to unmask]>[log in to unmask]<mailto:[log in to unmask]>> wrote:
Hello,
I would like to know how can I know the direccion of one correlation in SPM. For example, if I put "1" on one variable of interest and "-1" into another variable does it means that there is a negative correlation between both variables?
Thanks in advance,
Kelly
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