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Thanks McLaren! I found a paper: Correcting for non-sphericity in imaging data using classical and Bayesian approaches<http://apps.isiknowledge.com/full_record.do?product=UA&search_mode=GeneralSearch&qid=1&SID=3D1mJp56p65no2aMEf3&page=1&doc=1&colname=WOS&cacheurlFromRightClick=no> Glaser, D E; Penny, W D; Henson, RN, et al. NEUROIMAGE V13(6) S127-S127 2001 It mentioned this problem but I am not sure. I am new to SPM. Anyhow, if this correcting won't hurt the analysis I won't have problems with it. Thanks again. Xin On Tue, Apr 6, 2010 at 3:07 PM, MCLAREN, Donald <[log in to unmask]>wrote: > Since standard statistics use a different formula for equal versus unequal > variance and SPM only is programmed to use the equal variance formula, this > is a way to account for the unequal variance. I'm not sure about the math > behind it, but trust that is works. > > 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 Tue, Apr 6, 2010 at 1:51 PM, Xin Chen <[log in to unmask]> wrote: > >> Thanks a lot for your reply! Could you please educate me a little bit more >> on this? How should I deal with it? Thanks again! >> >> Xin >> >> >> On Tue, Apr 6, 2010 at 2:44 PM, MCLAREN, Donald <[log in to unmask] >> > wrote: >> >>> This is an effect of setting the conditions to unequal variance. >>> >>> 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 Tue, Apr 6, 2010 at 1:33 PM, Xin Chen <[log in to unmask]> wrote: >>> >>>> Dear Friends of SPM, >>>> >>>> I was doing a simple 2nd level analysis, paired T test to be specific. >>>> The design matrix looks fine before I ran the spm5 estimation, please see >>>> the attached beforeestimate.jpg. However, after the estimation the design >>>> matrix changed somehow, please see the afterestimate.jpg, it turned a little >>>> bit gray but not clear cut black/white. I am wondering is it just a graphic >>>> artifact of spm5, or I did something wrong? Or spm5 adjusted my original >>>> design matrix because of some weakness of my data? >>>> >>>> Thanks in advance. >>>> >>>> Xin >>>> >>>> >>>> >>>> >>>> Xin Chen Ph.D. >>>> Brain and Behavior Discovery Institute >>>> Medical College of Georgia >>>> >>>> >>> >> >> >> -- >> Xin Chen Ph.D. >> Brain and Behavior Discovery Institute >> Medical College of Georgia >> >> > -- Xin Chen Ph.D. Brain and Behavior Discovery Institute Medical College of Georgia