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Dr van Dongen-Boomsma Replies

J Clin Psychiatry 2014;75(7):779 [letter]

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To the Editor: My colleagues and I thank Dagenais and colleagues for their detailed letter, in which they ask for clarification of the following statement: “Post hoc, our sample had 80% power to detect a treatment effect of 0.90 . . . it is unlikely that our negative results were due to limited statistical power.” Hopefully, this letter will answer their questions.

First, we appreciate Dagenais and colleagues’ acknowledgment regarding the robust methodological design of our study. Further, we thank them for pointing out an error in the text. Although we actually did have an 80% power to detect a treatment effect of 0.90, the power to detect rather small differences between EEG neurofeedback and placebo neurofeedback indeed was much more limited, namely between 5% and 11%, as they show.