Number of events and reliability in fMRI
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Relatively early in the history of fMRI, research focused on issues of power and reliability, with an important line concerning the establishment of optimal procedures for experimental design in order to maximize the various statistical properties of such designs. However, in recent years, tasks wherein events are defined only a posteriori, on the basis of behavior, have become increasingly common. Although these designs enable a much wider array of questions to be answered, they are not amenable to the tight control afforded by designs with events defined entirely a priori, and little work has assessed issues of power and reliability in such designs. We demonstrate how differences in numbers of events—as can occur with a posteriori event definition—affect reliability, both through simulation and in real data.
KeywordsNeuroimaging Design and analysis Statistical power
This research was supported by the Institute for Collaborative Biotechnologies through Grant No. W911NF-09-D-0001 from the U.S. Army Research Office. The content of the information does not necessarily reflect the position or the policy of the Government, and no official endorsement should be inferred.
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