I have a clarifying question about fsgd file format.<div>We have 40 participants, and a large battery of individual difference measures (egg., vocabulary, phonological skill, etc.)</div><div>We applied a PCA to the battery and found 4 components, corresponding to WMC, processing speed, comprehension ability, and phonological ability.</div>
<div>We tested for main effects of each of these on thickness, area, and volume via QDEC.</div><div>However, we also want to check for interactions - and since this is essentially 4 continuous factors, this is not QDEC-able (at least, it does not appear to be). A nuisance variable (e.g., mean thickness) is also present.</div>
<div><span style="font-size:small">Nregressors = Nclasses*(Nvariables+1) = 1*((4 components + 1 nuisance) +</span><span style="font-size:small">1) = 1*(5+1) = 6</span><br></div><div><span style="font-size:small"><br></span></div>
<div><span style="font-size:small">Null contrast is </span></div><div><span style="font-size:small">1 0 0 0 0 0</span></div><div><span style="font-size:small"><br></span></div><div><span style="font-size:small">Main effect, e.g., of the working memory component (#1) is</span></div>
<div><span style="font-size:small"><br></span></div><div><span style="font-size:small">0 1 0 0 0 0</span></div><div><br></div><div>Main effect, e.g., of the WM component modulated by the nuisance variable is</div><div><br>
</div><div>0 1 0 0 0 1</div><div><br></div><div>So the format to examine possible interactions, e.g., component 1 and component 2 interact to affect thickness, is</div><div><br></div><div>0 1 1 0 0 0</div><div><br></div><div>
And with the nuisance variable</div><div><br></div><div>0 1 1 0 0 1</div><div><br></div><div>Do we have this right?</div><div><br></div><div>THANKS!!</div><div><br></div><div>Clint</div><div><br></div><div><br></div><div>
<br></div><div><br><br></div><br><br>-- <br><div dir="ltr">I remain...<br><br>Clinton L. Johns, Ph.D.<br>Research Scientist, Haskins Laboratories<br>300 George Street<br>New Haven     CT     06511<br>speech:     203-865-6163 x240<br>
fax:     203-865-8963<br>net:     <a href="mailto:johns@haskins.yale.edu" target="_blank">johns@haskins.yale.edu</a></div><br>