The median is a more robust statistic (i.e., less sensitive to outliers and asymmetry of distributions) than the mean, so it makes sense to compare medians rather than means. The problem with taking a ratio is that your control values are too small; single digits on an RFI scale of 1-10000 are likely to represent measurements dominated by noise. Differences between medians on a log scale are, in effect, ratios, and present the same problem. The difference between medians on the linear RFI scale is probably a safe measure. -Howard
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