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</o:shapelayout></xml><![endif]--></head><body lang="EN-CA" link="#0563C1" vlink="#954F72"><div class="WordSection1"><p><span style="font-size:12.0pt;font-family:"Times New Roman",serif">Hello,<o:p></o:p></span></p><p><span style="font-size:12.0pt;font-family:"Times New Roman",serif">I was wondering if I could ask a clarification question about the correct interpretation of the outputs of Fieldtrip’s ft_timelockstatistics function?<o:p></o:p></span></p><p><span style="font-size:12.0pt;font-family:"Times New Roman",serif">Online, it says:<o:p></o:p></span></p><p><span style="font-size:12.0pt;font-family:"Times New Roman",serif">“We use cfg.alpha to control the false alarm rate of the permutation test (the probability of falsely rejecting the null hypothesis). The value of cfg.alpha determines the critical values with which we must compare the test statistic (i.e., the maximum and the minimum cluster-level statistic). Note that if you want to run a two-sided test, you have to split the critical alpha value by setting cfg.correcttail = ‘alpha’; i.e. this sets cfg.alpha = 0.025, corresponding to a false alarm rate of 0.05 in a two-sided test. The field cfg.alpha is not crucial. This is because the output of ft_timelockstatistics (see further) contains a p-value for every cluster (calculated under the permutation distribution of the maximum/minimum cluster-level statistic). Instead of the critical values, we can also use these p-values to determine the significance of the clusters.”<o:p></o:p></span></p><p><span style="font-size:12.0pt;font-family:"Times New Roman",serif">I interpreted this to mean that I should double all the p-values I get in the final output, since I am running two-tailed tests. E.g., if I specify that I want a two-tailed test in cfg.tail and if I then get an output saying:<o:p></o:p></span></p><p><span style="font-size:12.0pt;font-family:"Times New Roman",serif">stat.posclusters<br>ans =<br>struct with fields:<br>prob: 0.0188<br>clusterstat: 160.9688<br>stddev: 0.0014<br>cirange: 0.0027<o:p></o:p></span></p><p><span style="font-size:12.0pt;font-family:"Times New Roman",serif">Then I interpret it to mean that the actual two-tailed p-value is 0.0376, not 0.0188. However, I’m having second thoughts about this, and wondering if I have this right.<o:p></o:p></span></p><p><span style="font-size:12.0pt;font-family:"Times New Roman",serif">I’m afraid this is kind of urgent – I’m supposed to submit slides tomorrow for a talk I’m giving where we analyze data using this function, so if you have a chance to confirm whether I am interpreting this correctly or not, that would be super-appreciated! Thanks so much,<o:p></o:p></span></p><p><span style="font-size:12.0pt;font-family:"Times New Roman",serif">Patrick<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif"><o:p> </o:p></span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-language:EN-CA">Patrick Dwyer<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-language:EN-CA">Ph.D. Student, Developmental Psychology<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-language:EN-CA"><a href="http://riveralab.ucdavis.edu/">Neurocognitive Development Lab</a><o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-language:EN-CA">Center for Mind and Brain, UC Davis<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-language:EN-CA"><o:p> </o:p></span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-language:EN-CA">Personal Blog: <a href="http://www.autisticscholar.com/">http://www.autisticscholar.com/</a><o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-language:EN-CA">Pronouns: he/him/his<o:p></o:p></span></p></div></body></html>