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(Stroke. 2008;39:e30.)
© 2008 American Heart Association, Inc.

Letters to the Editor

Response to Letter by Cloft and Kallmes

Department of Neuroradiology, University of Wuerzburg, Wuerzburg, Germany

Christian F. Beckmann, DPhil

Department of Clinical Neurosciences, Imperial College London, London, UK

László Solymosi, MD

Department of Neuroradiology, University of Wuerzburg, Wuerzburg, Germany

Martin Bendszus, MD

Department of Neuroradiology, University of Heidelberg, Heidelberg, Germany

An extract of the first 250 words of the full text is provided, because this article has no abstract.

Response:

We appreciate the comment by Drs Cloft and Kallmes on our recent article regarding the matched-pair evaluation of a new bioactive coil.¹ It provides us with the opportunity to briefly clarify the statistical analysis and the rationale behind it. This will illustrate why the statistical analysis of the data presented in this article is accurate and not erroneous. We have indeed used a 1-sided Fisher exact test for comparison of the 6-month follow-up occlusion rates. For statistical inference, ie, the confidence that our reported results do in fact detect a true-positive increase of follow-up occlusion rates with Cerecyte compared with bare platinium coils, this is important, especially because for comparison of the initial treatment results a 2-sided test was performed.

However, we do not agree that this corresponds to a "basic statistical error" and that the use of a 1-sided test for comparison of the follow-up occlusion rates would be "inappropriate", as claimed by Drs Cloft and Kallmes. Without wanting to delve too deep into the philosophy of significance testing (see reference ² for a more in-depth discussion), it appears well established that it is largely uninterpretable to ascertain the "true value" of false-positive probability rates, ie, probability values and significance levels, without a specific null-hypothesis and specific assumptions about the deviation in the data from it. It is largely misleading to claim that 2-sided testing is simply "more conservative" compared with 1-sided statistical inference: both utilize the same null-hypothesis and test the value of a given test statistic under . . . [Full Text of this Article]