<p></p>
<h2><span style="color: rgb(82, 96, 105); font-size: 1rem; font-family: &quot;Open Sans&quot;, sans-serif;">When gathering data, the clinician
must begin with visual analysis of the data and proceed to edit the EEG
information, removing all artifacts and, if they are persistent or
unremovable,&nbsp; denoting how they will
affect the qEEG, so as to not misinterpret the artifactual findings as real.</span><br></h2>

<h2><a name="_Toc35418100">Impedance</a></h2>

<p>Typically, when gathering QEEG data, the clinician starts by ensuring the electrodes have a low impedance. They might use a checktrode impedance meter or another built-in impedance checking system. </p>
<p>Here is short video on checking impedance with Neurofield software:&nbsp;&nbsp;&nbsp;<video controls="true"><source src="https://www.youtube.com/watch?v=OPof2CEqYq8">https://www.youtube.com/watch?v=OPof2CEqYq8</video>&nbsp;</p>
<h2><a name="_Toc35418101"></a><a name="_Toc3535259">QEEG databases</a> </h2>

<p>Many quantitative EEG Databases use Z-scores to measure how deviant the individual is from the normal population, in terms of amplitude/magnitude (often referred to as “power”), coherence, phase measures, and symmetry. </p>
<p>Here is a short video of Bob Thatcher describing the creation of Z-Scores:</p>
<div style="padding:56.25% 0 0 0;position:relative;"><iframe src="https://player.vimeo.com/video/429334628?h=19c30c8de6&amp;badge=0&amp;autopause=0&amp;player_id=0&amp;app_id=58479" frameborder="0" allow="autoplay; fullscreen; picture-in-picture" allowfullscreen="" style="position:absolute;top:0;left:0;width:100%;height:100%;" title="THATCHER - Z SCORE (with intro and outro)"></iframe></div><script src="https://player.vimeo.com/api/player.js"></script>
<p><b><u>Z scores</u></b></p>

<p>Z = subject value – mean value of the same/ SD of the sample</p>

<p>Z= probability that the subject value lies within the normal range. 1.96 Z scores is 2 SDs.</p>
<h3>Image of a bell curve denoting Z-scores&nbsp;</h3>
<p style="text-align: center;"><span style="font-size: 1rem;">&nbsp;</span><img src="@@PLUGINFILE@@/Z-score%20chart.jpg" alt="z scores" width="546" height="368" class="img-responsive atto_image_button_middle" style="font-size: 1rem; text-align: center;"></p>
<p></p>