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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Dear Irene,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">If your research question is whether there is a difference in global mean field power between conditions I would approach this in the same way as if you would
want to investigate a difference in ERF/ERPs between conditions. You would therefore first calculate the time-locked averages for both conditions for each participant separately, as you did. The you would calculate the global mean field power using ft_globalmeanfield
for both conditions, for each participant. If I’m not mistaken you can calculate the group average using ft_timelockgrandaverage. You could test the difference between conditions using dependent samples t-tests (perhaps cluster corrected over time) using ft_timelockstatistics.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Best,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Jim<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> fieldtrip-bounces@science.ru.nl [mailto:fieldtrip-bounces@science.ru.nl]
<b>On Behalf Of </b>Irene Sophia Mayer<br>
<b>Sent:</b> Sunday, February 21, 2016 1:15 PM<br>
<b>To:</b> fieldtrip@science.ru.nl<br>
<b>Subject:</b> [FieldTrip] Global field power<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Verdana",sans-serif">Dear fieldtrippers, <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Verdana",sans-serif"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Verdana",sans-serif">I want to compare the global field power in two different conditions over several participants. I have computed time-locked averages for both conditions for each participant
separately. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Verdana",sans-serif"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Verdana",sans-serif">My first question now is, should I first compute a grand average over all participants and use
<o:p></o:p></span></p>
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<pre style="margin-bottom:12.0pt;text-align:justify;background:#F7F9FA;border:none;padding:0in"><span style="font-size:9.0pt;font-family:Consolas">ft_globalmeanfield<o:p></o:p></span></pre>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Verdana",sans-serif">on this or should I first compute global mean field for every participant and then average over them? Additionally, which functions should I use for those kinds of averaging?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Verdana",sans-serif"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Verdana",sans-serif">The second question would be, has anyone any recommendations for a statistical test I could use to see whether the conditions differ in global mean field power?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Verdana",sans-serif"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Verdana",sans-serif">Cheers, <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Verdana",sans-serif">Irene<o:p></o:p></span></p>
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