Reply-To: | | [log in to unmask][log in to unmask]">[log in to unmask] > ca</a>> > wrote:<o:p></o:p></span></font></p> > > <div link=3Dblue vlink=3Dpurple> > > <div> > > <p><font size=3D2 face=3DArial><span = > style=3D'font-size:10.0pt;font-family:Arial'>Hi > everyone,</span></font><o:p></o:p></p> > > <p><font size=3D2 face=3DArial><span = > style=3D'font-size:10.0pt;font-family:Arial'>I've > run into an analysis question that I don't understand. I am looking over = > books > and the email list but I'm wondering if anyone has any ideas to at least = > get me > started in the right direction.</span></font><o:p></o:p></p> > > <p><font size=3D2 face=3DArial><span = > style=3D'font-size:10.0pt;font-family:Arial'> </span></font><o:p></o= > :p></p> > > <p><font size=3D2 face=3DArial><span = > style=3D'font-size:10.0pt;font-family:Arial'>I've > done two analyses on one individual. The data were acquired with 3.75 x = > 3.75 x > 6 mm voxels. In the first analysis, I normalized to the standard brain = > and > resampled to 3 x 3 x 3 mm voxels. In the second analysis, I skipped the > normalization and maintained the original voxel size. In both analyses, = > I > applied a smoothing kernel of 7.5 x 7.5 x 7.5 mm FWHM. In fact all of = > the other > preprocessing steps and options in the statistical analysis were exactly = > the > same. The only difference is which data I input into the model = > (normalized or > unnormalized).</span></font><o:p></o:p></p> > > <p><font size=3D2 face=3DArial><span = > style=3D'font-size:10.0pt;font-family:Arial'> </span></font><o:p></o= > :p></p> > > <p><font size=3D2 face=3DArial><span = > style=3D'font-size:10.0pt;font-family:Arial'>The > SPM results indicate a smoothness of 31.0 x 35.5 x 27.2 mm FWHM for the > unnormalized analysis, and 14.6 x 14.7 x 16.4 mm FWHM for the normalized > analysis (does this mean my unnnormalized images are smoother? This is > confusing to me, it seems to me that the upsampling done in the = > normalization > step would have a smoothing effect as voxels are = > interpolated).</span></font><o:p></o:p></p> > > <p><font size=3D2 face=3DArial><span = > style=3D'font-size:10.0pt;font-family:Arial'> </span></font><o:p></o= > :p></p> > > <p><font size=3D2 face=3DArial><span = > style=3D'font-size:10.0pt;font-family:Arial'>The > major concern is that I lose a lot of power in the unnormalized = > analysis. The > two analyses look about the same when I set the threshold to p <0.05 = > FWE > corrected in the normalized analysis and p < 0.05 uncorrected in the > unnormalized analysis.</span></font>&®λΥ: |