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Figure 3 Sequential analysis plot. Results of the sequential monitoring procedure used to determine the stopping point for the study, based on the primary end point of first-shock efficacy. The horizontal axis shows the V statistic, a measure of the total information contained within the data at each interim analysis. The vertical axis shows the Z statistic, a measure of the difference between the groups. The study is terminated when one of the three boundaries is crossed. In this case, the study was stopped after the 10th analysis because the results crossed the boundary for statistical equivalence between the two groups.