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</o:shapelayout></xml><![endif]--></head><body lang=NL link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'>Dear Maya,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div style='border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt'><div><div><p class=MsoNormal><span lang=EN-US>I was recently referred to your paper on the subject of nonparametric statistical testing in Journal of Neuroscience Methods (2007). <br></span>I find the paper very interesting and it has contributed a lot to the statistical analyses I'm currently using. <br> <br>My experiment includes 3 conditions, of which I was a priori interested in two. Thus, I ran the analysis proposed by you for two of the conditions only that were of relevant theoretical interest, and found significant differences at a specific time window and cluster of electrodes. Now I'm interested in examining the third condition at this specific time and space frame. I was wondering if you could advise what would the appropriate statistical threshold/correction be, as I'm unsure after consulting several of my colleagues.<o:p></o:p></p></div><div><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'>I see the following options:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span lang=EN-US style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span lang=EN-US style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'>Compare the third condition with each of the other two conditions and do Bonferroni-correction to account for the fact that you perform three tests.<o:p></o:p></span></p><p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span lang=EN-US style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span lang=EN-US style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'>Compare all three conditions with a cluster-based permutation test using an F-statistic statfun (depsamplesF for a within-UO design and indepsamplesF for a between-UO design). The power of this test will be somewhat lower than the power of the cluster-based permutation test using the t-statistic that you have already performed.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'>Examining the difference between the third condition and the first two at the data-selected time and space frame does not in general control the false alarm rate (because the selection of the time and space frame is based on the data).<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'>Best,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'>Eric<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D'><o:p> </o:p></span></p></div></div></div></div></body></html>