Hello everyone,<br><br>I created a qdec.table.dat for my design (a simple group analysis, with gender as categorical factor and age as continuous factor), and created a gender.levels file containing the values that are found in qdec.table.dat, spellt in exactly the same way (all files attached). However, when loading the file in QDEC, I get the error:<br>

<br><div style="margin-left:40px"><i>ERROR: Subject C01 has an invalid level &#39;controls&#39; in the group column<br>INFO: If &#39;group&#39; is a discrete factor, then create a file named &#39;group.levels&#39; containing the valid factor names one per line.<br>

Error loading the data table.<br></i></div><br>The strings under the fsid column (subject ID) correspond to those that I
 used after the –subjid xxx, in my previous call to recon-all (e.g. &quot;C01, C02, M01, M02..&quot;). The qdec.table.dat was created in Excel and saved as a tab-delimited txt file. Replacing the tabs with spaces/commas does not change the error message. What could be the problem?<br>

<br><br>I also have a few more questions, if I may:<br><br>- how much more accurate are the results of a QDEC analysis if an average subject is computed from the subjects of the sample, with make_average_subject, as opposed to using FS&#39;s default average subject, fsaverage?<br>

<br>- the qdec.table.dat in the <a href="http://surfer.nmr.mgh.harvard.edu/fswiki/FsTutorial/QdecGroupAnalysis">tutorial </a>contains more than just &quot;demographical information&quot;, for instance it contains the volumes of the left and right hippocampi; are these types of informations normally brought in from previous analyses (that may have been done in a package other than FS), or does one first have to obtain any such relevant predictors in FreeSurfer, before starting the QDEC analysis?<br>

<br>- the QDEC tutorial seems to be for whole-brain analyses; the <a href="http://surfer.nmr.mgh.harvard.edu/fswiki/FsTutorial/AnatomicalROI">ROI analysis tutorial</a> mentions nothing of QDEC, however; can ROI analyses not also be done in QDEC?<br>

<br>- in the Group Analysis (non-QDEC) <a href="http://surfer.nmr.mgh.harvard.edu/fswiki/FsTutorial/GroupAnalysis">tutorial</a>, the design matrix (Xg.dat) is in the form MembershipF| MembershipM|AgeF|AgeM, while the values in the contrast are said to correspond to the 4 parameters (intercept for F,M; slope for F,M). Either way, how can the contrast vector be interpreted to give the correlation between thickness and age?<br>

<br>- in the same tutorial, why is the value 0 being given to the first two elements in the matrix, when it should only be given to nuisance variables?<br><br>Many thanks in advance for any help!<br>Tudor<br>