However, to provide strong evidence for such a conclusion, either a statistical comparison of group effect sizes of the ERO and ERP measures is required or an analysis of covariance should be undertaken to assess whether the variance of the ERO power measures remaining, after the covariance between the ERP and ERO measures is removed, significantly discriminates the two groups. Such methods were not applied in the Jones et al. (2006) and Rangaswamy et al. (2007) studies (group effect sizes were not even presented), and so the conclusions made were not supported by quantitative analysis.
