<p><span style="font-size: 1rem;">Information in this description taken from -&nbsp;</span><i style="font-size: 1rem;">"Use of Databases in QEEG Evaluation, Jack Johnstone, PhD &amp; Jay Gunkelman, QEEG-D"</i><br></p><p>The SKIL database currently includes 135 adults ranging from 18 to 55 years old (see Sterman &amp; Kaiser, 2001). No normative information is currently available for children or young adults. SKIL does not consider age as a factor in computing z-score deviations. The reference population is comprised of students and laboratory personnel (50%), volunteers recruited from the community (25%), and U.S. Air Force personnel (25%). Screening was based on questionnaire regarding medical history, drug use, and recent life events.</p><p>The SKIL database incorporates recordings at rest (eyes closed and open) and during task&nbsp; challenges involving audio-visual information processing and visual-spatial tracking. A correction for the time of day of recording is available which is based on combined cross-sectional and longitudinal data rather than the preferred method of tracking within-subject changes over time.&nbsp; The SKIL database covers a restricted range of frequencies, from 2 Hz to 25 Hz. This method deletes signiﬁcant slow and fast frequency data which may be of clinical importance. However, the database does have the advantage of providing norms for each single Hz increment over this frequency range. The SKIL database relies exclusively on the linked ear reference. The SKIL analysis has not received FDA 510(k) clearance and is labeled as “not intended for medical use.”&nbsp;</p><p>The SKIL database does not have a measure of EEG coherence but rather includes a similarity measure termed“comodulation,” which is quite like coherence but does not yield a measure of phase.&nbsp; Comodulation is essentially the correlation of the spectrum for two recording electrodes over time using a sliding one second data window moved in 250 millisecond increments. Although this effectively deals with windowing issues, it also is clear that the degree of correlation between electrode sites is not computed on independent, but rather overlapping, spectral analyses.&nbsp;</p><p>Since the SKIL database relies exclusively on the linked ear reference, the comodulation similarity measure is strongly inﬂuenced by the fact that both sites are connected to a common source. This can lead to shared variance, which can cause erroneous comodulation results. Nevertheless, the comodulation metric is currently being explored for possible clinical utility.&nbsp;</p><p>As discussed previously, there must be a balance between the number of individuals in a database and the number of variables used in assessment to account for multiple statistical tests. The SKIL database has the advantage of a large number of features (e.g., multiple conditions, 1 Hz bins) but has the disadvantage of a relatively small number of individuals represented in the database. This tends to increase the number of false positive ﬁndings. A solution to the problem of false positive results is to replicate ﬁndings on independent samples of data from the individual patient.</p><p style="text-align: center;"><img src="@@PLUGINFILE@@/brands-of-power-skill.png" alt="Image of Bands of Power in SKIL" width="538" height="439" class="img-responsive atto_image_button_text-bottom"><br></p><p style="text-align: center;">Figure #1 Image of Bands of Power in SKIL<br></p><p style="text-align: center;"><br></p><p style="text-align: center;"><img src="@@PLUGINFILE@@/unity-measure-skil.png" alt="Image of Theta Unity measure in SKIL" width="627" height="586" class="img-responsive atto_image_button_text-bottom"><br></p><p style="text-align: center;">Figure #2&nbsp;Image of Theta Unity measure in SKIL</p><p style="text-align: center;"><br></p><p style="text-align: center;"><img src="@@PLUGINFILE@@/skill-img-spectra.png" alt=" Image of spectra at each site from SKIL" width="677" height="352" class="img-responsive atto_image_button_text-bottom"><br></p><p style="text-align: center;">Figure #3 -&nbsp;Image of spectra at each site from SKIL</p>