deletions | additions       diff --git a/We_needed_to_emphasize_that__.tex b/We_needed_to_emphasize_that__.tex  index 9ef8874..d3ac4b8 100644  --- a/We_needed_to_emphasize_that__.tex  +++ b/We_needed_to_emphasize_that__.tex 
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We needed to emphasize that the The  number of phantom subjects do not contribute to the power equation in Figure 1. The power equation we that was  derived does not account for any sort of calibration or scaling. Instead, it requires an estimate for $CV_a$, which is the variability of scaling biases between sites. Because we are not asking our Our  consortium was not asked  to change protocols, we thought that our so the  true bias  variability would certainly might  be higher than that of a harmonized study, and sample sizes we would calculate would be smaller than we what is  actually need needed  ifwe used  harmonized data was used  to calculate it. bias.  For other researchers planning multisite studies,they could use  our measurements of $CV_a$ could be used  to get a better power estimates if the estimate for  protocols in their consortiums that  are close to the 3D-MPRAGE protocols that were  described here. This is especially useful if they want to include for the inclusion of  retrospective data in their analyses. data.  To power an estimate of $CV_a$, we'd need enough subjects to get accurate estimates of scaling factors within sites, two sample sizes are required - the subject level,  and enough sites to get a better variance estimates. the site level.  The sample size of 12 is enough to estimate the slope of the calibration line (which is around 1), because the scan-rescan reliability of the ROIs is very high. high (around 0.9).  Ideally, we would have more than 12 subjects to get better a better estimate of the intercept (This is intercept, and this was  listed as a study limitation in the discussion). We sampled from discussion.  20 sites were sampled  because these same sites will be used in a future study on MS genetics and MRI phenotypes, although the inclusion of more sites would also improve the $CV_a$ estimate. In the text, we've it was  emphasized that the derived power equation does not require phantom subjects or calibration to be used: "\textit{We emphasize that the use of phantom subjects do not directly contribute to the power equation in Figure 1, as it does not account for any sort of calibration or scaling. However, it requires an estimate for $CV_a$, which is the variability of scaling biases between sites. The goal of this study is to provide researchers with estimates of $CV_a$ from our set of calibration phantoms and our set of non-standardized MRI acquisitions. For a standardized set of scanners, these values may be considered an upper bound. }"