Natalie, It's best to provide at least a sample of your data. Your field names suggest that your data might be collected in units of mm^2 or some similar measurement of area. Why do you want to use Mann-Whitney, which will rank your data and then use those ranks rather than your actual data? Unless your sample is quite small, why not use a two sample t-test? Also,are your samples paired? If they aren't, did you use the "paired = FALSE" option?
JWDougherty ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
