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<div>Dear Arno,</div>
<div><font face="tahoma">that is what I've expected but how can one then compare powers between two group ( looking at a peak frequency of e.g. two groups of patients) being sure that the difference does not come from individual difference in EEG amplitude?</font></div>
<div><font face="tahoma">Or other way around, how can we replace a value of the absolute power in a STUDY with the relative power and then visualise it using the<a></a> STUDY tools?</font></div>
<div><font face="tahoma">Many thanks,</font></div>
<div><font face="tahoma">Aleksandra</font></div>
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<font color="#000000" size="2" face="Tahoma"><b>From:</b> Arnaud Delorme [arno@ucsd.edu]<br>
<b>Sent:</b> 12 October 2012 02:28<br>
<b>To:</b> Aleksandra Vuckovic<br>
<b>Cc:</b> tarikbelbahar@gmail.com; M Abul Hassan; eeglablist@sccn.ucsd.edu<br>
<b>Subject:</b> Re: [Eeglablist] Is power calculated in STUDY and in dataset is abs or relative?<br>
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<div>Dear Aleksandra,
<div><br>
</div>
<div>power is absolute when plotting the spectrum and relative to baseline when computing ERSP as Tarik mentioned.</div>
<div>Best,</div>
<div><br>
</div>
<div>Arno</div>
<div><br>
<div>
<div>On 9 Oct 2012, at 01:48, Aleksandra Vuckovic wrote:</div>
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<div style="FONT-FAMILY: Tahoma; DIRECTION: ltr; COLOR: rgb(0,0,0); FONT-SIZE: x-small">
<div>Hi,</div>
<div><font face="tahoma">what Abul<a></a><a></a> Hasan<a></a><a></a><span class="Apple-converted-space"> </span>is asking is whether the Power calculated in EEGLab<a></a><a></a><span class="Apple-converted-space"> </span>in certain frequency<a></a> band<a></a><span class="Apple-converted-space"> </span>is
absolute or relative (e.g. for example is it Power (8-12 Hz) or Power (8-12 Hz)/Power(1-40 Hz) )</font></div>
<div><font face="tahoma">This is a relevant question if one wants to compare mean Power values between two groups in a STUDY. We need to be sure that the difference is not coming from the fact that people in one group have a higher amplitude EEG but that their
relative power in certain frequency band is higher as compare to the other group.</font></div>
<div><font face="tahoma">Can anybody give us a clue how to get a relative power using STUDY so we can use all nice graphical presentation and statistics?</font></div>
<div><font face="tahoma"></font> </div>
<div><font face="tahoma">Many thanks,</font></div>
<div><font face="tahoma">Aleksandra</font></div>
<div><font face="tahoma"></font> </div>
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<font color="#000000" size="2" face="Tahoma"><b>From:</b><span class="Apple-converted-space"> </span><a href="mailto:eeglablist-bounces@sccn.ucsd.edu">eeglablist-bounces@sccn.ucsd.edu</a><span class="Apple-converted-space"> </span>[<a href="mailto:eeglablist-bounces@sccn.ucsd.edu">eeglablist-bounces@sccn.ucsd.edu</a>]
On Behalf Of Tarik S Bel-Bahar [<a href="mailto:tarikbelbahar@gmail.com">tarikbelbahar@gmail.com</a>]<br>
<b>Sent:</b><span class="Apple-converted-space"> </span>08 October 2012 22:41<br>
<b>To:</b><span class="Apple-converted-space"> </span>M Abul Hassan<br>
<b>Cc:</b><span class="Apple-converted-space"> </span><a href="mailto:eeglablist@sccn.ucsd.edu">eeglablist@sccn.ucsd.edu</a><br>
<b>Subject:</b><span class="Apple-converted-space"> </span>Re: [Eeglablist] Is power calculated in STUDY and in dataset is abs or relative?<br>
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<div>Greetings Abdul,
<div><br>
</div>
<div>I am not an expert on the mechanics here,</div>
<div>but I believe if you are referring to ERSP computation using the newtimef function,</div>
<div>then the baseline of values before the 0 time point in your epochs is automatically subtracted.</div>
<div>Please also see multiple messages on this topic in recent months in the eeglablist archives.</div>
<div><br>
</div>
<div>Respectfully,</div>
<div>Tarik</div>
<div><br>
</div>
<div><br>
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<div><br>
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<br>
<div class="gmail_quote">On Fri, Oct 5, 2012 at 2:37 AM, M Abul Hassan<span class="Apple-converted-space"> </span><span dir="ltr"><<a href="mailto:abulhassan85@yahoo.com">abulhassan85@yahoo.com</a>></span><span class="Apple-converted-space"> </span>wrote:<br>
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<div>Dear all</div>
<div> </div>
<div>I want to know the power spectrum generated by EEGLAB both in a STUDY and in each dataset seperately is using absolute values or relative values.</div>
<div> </div>
<div>If it based on relative values than how a frequency range can be known?</div>
<div> </div>
<div>If it is based on absolute values than how can I calculate the relative power in EEGLAB?</div>
<div> </div>
<div>Thanks</div>
<div>Best Regards</div>
<div>Muhammad Abul Hasan</div>
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