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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 ================= D.G. McLaren University of Wisconsin - Madison Neuroscience Training Program Office: (608) 520-0586 ===================== This e-mail contains CONFIDENTIAL INFORMATION which may contain PROTECTED HEALTHCARE INFORMATION and may also be LEGALLY PRIVILEGED and which is intended only for the use of the individual or entity named above. If the reader of the e-mail is not the intended recipient or the employee or agent responsible for delivering it to the intended recipient, you are hereby notified that you are in possession of confidential and privileged information. Any unauthorized use, disclosure, copying or the taking of any action in reliance on the contents of this information is strictly prohibited and may be unlawful. If you have received this e-mail unintentionally, please immediately notify the sender via telephone at (608) 520-0586 or email. On Fri, Jan 29, 2010 at 3:03 AM, Kelly Atalaia Silva < [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 >